diff --git a/.github/linters/.eslintrc.yml b/.github/linters/.eslintrc.yml
index 7f660fc..0d90eec 100644
--- a/.github/linters/.eslintrc.yml
+++ b/.github/linters/.eslintrc.yml
@@ -42,6 +42,7 @@ rules:
     'i18n-text/no-en': 'off',
     'import/no-namespace': 'off',
     'no-console': 'off',
+    'no-shadow': 'off',
     'no-unused-vars': 'off',
     'prettier/prettier': 'error',
     'semi': 'off',
@@ -63,6 +64,7 @@ rules:
     '@typescript-eslint/no-misused-new': 'error',
     '@typescript-eslint/no-namespace': 'error',
     '@typescript-eslint/no-require-imports': 'error',
+    '@typescript-eslint/no-shadow': 'error',
     '@typescript-eslint/no-unnecessary-qualifier': 'error',
     '@typescript-eslint/no-unnecessary-type-assertion': 'error',
     '@typescript-eslint/no-unused-vars': 'error',
diff --git a/README.md b/README.md
index 590132d..a0078f5 100644
--- a/README.md
+++ b/README.md
@@ -157,6 +157,6 @@ sizeup:
 
 The default configuration that is used when no configuration file is provided can be found in [`src/config/default.yaml`](./src/config/default.yaml).
 
-The full specification for the configuration file is provide by the JSON schema at [`src/config/schema.json`](./src/config/schema.json).
+The full specification for the configuration file, which includes options that are not specified in the example above or in the default configuration, is provided by the JSON schema at [`src/config/schema.json`](./src/config/schema.json).
 
 For details about what configuration can be provided under the `sizeup` key, please see the [`sizeup-core` library's configuration guide](https://github.com/lerebear/sizeup-core#configuration).
diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
index c3a8273..cf0a5e4 100644
--- a/__tests__/main.test.ts
+++ b/__tests__/main.test.ts
@@ -145,6 +145,28 @@ describe('action', () => {
     )
   })
 
+  it('skips labelling a pull request when running in shadow mode', async () => {
+    // Mock the @actions/github context.
+    Object.defineProperty(github, 'context', {
+      value: pullRequestEventContext()
+    })
+
+    loadConfigurationMock.mockImplementation(() => ({
+      // Mock config such that the only opted-in user is @glortho. The pull request will be created
+      // by @lerebear, who should therefore *not* be considered opted in.
+      optIns: ['glortho'],
+      shadowOptOuts: true
+    }))
+
+    await main.run()
+
+    expect(runMock).toHaveReturned()
+    expect(setFailedMock).not.toHaveBeenCalled()
+    expect(infoMock).toHaveBeenCalledWith(
+      'Skipping labeling because this workflow is running in shadow mode'
+    )
+  })
+
   it('skips commenting on a draft pull request when configured to do so', async () => {
     // Mock the @actions/github context.
     Object.defineProperty(github, 'context', {
@@ -164,6 +186,29 @@ describe('action', () => {
     )
   })
 
+  it('skips commenting on a pull request when running in shadow mode', async () => {
+    // Mock the @actions/github context.
+    Object.defineProperty(github, 'context', {
+      value: pullRequestEventContext()
+    })
+
+    loadConfigurationMock.mockImplementation(() => ({
+      // Mock config such that the only opted-in user is @glortho. The pull request will be created
+      // by @lerebear, who should therefore *not* be considered opted in.
+      optIns: ['glortho'],
+      shadowOptOuts: true,
+      commenting: { scoreThreshold: 0 }
+    }))
+
+    await main.run()
+
+    expect(runMock).toHaveReturned()
+    expect(setFailedMock).not.toHaveBeenCalled()
+    expect(infoMock).toHaveBeenCalledWith(
+      'Skipping commenting because this workflow is running in shadow mode'
+    )
+  })
+
   it('runs the workflow sucessfully when optIns configuration is present and the pull request author is in it', async () => {
     // Mock the @actions/github context.
     Object.defineProperty(github, 'context', {
@@ -172,7 +217,7 @@ describe('action', () => {
 
     loadConfigurationMock.mockImplementation(() => ({
       // Mock config such that the only opted-in user is @glortho. The pull request will be created
-      // by @lerebear, who should therefore not be considered optedpin.
+      // by @lerebear, who should therefore *not* be considered opted in.
       optIns: ['lerebear']
     }))
 
diff --git a/badges/coverage.svg b/badges/coverage.svg
index 337ea38..a8068d8 100644
--- a/badges/coverage.svg
+++ b/badges/coverage.svg
@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="116" height="20" role="img" aria-label="Coverage: 64.96%"><title>Coverage: 64.96%</title><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="116" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="63" height="20" fill="#555"/><rect x="63" width="53" height="20" fill="#e05d44"/><rect width="116" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><text aria-hidden="true" x="325" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="530">Coverage</text><text x="325" y="140" transform="scale(.1)" fill="#fff" textLength="530">Coverage</text><text aria-hidden="true" x="885" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="430">64.96%</text><text x="885" y="140" transform="scale(.1)" fill="#fff" textLength="430">64.96%</text></g></svg>
\ No newline at end of file
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="116" height="20" role="img" aria-label="Coverage: 68.02%"><title>Coverage: 68.02%</title><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="116" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="63" height="20" fill="#555"/><rect x="63" width="53" height="20" fill="#e05d44"/><rect width="116" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><text aria-hidden="true" x="325" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="530">Coverage</text><text x="325" y="140" transform="scale(.1)" fill="#fff" textLength="530">Coverage</text><text aria-hidden="true" x="885" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="430">68.02%</text><text x="885" y="140" transform="scale(.1)" fill="#fff" textLength="430">68.02%</text></g></svg>
\ No newline at end of file
diff --git a/dist/config/schema.json b/dist/config/schema.json
index 1b5221e..49c1d38 100644
--- a/dist/config/schema.json
+++ b/dist/config/schema.json
@@ -59,6 +59,11 @@
                 "type": "string"
             }
         },
+        "shadowOptOuts": {
+            "description": "Whether or not to compute a score even for users who have opted out of the workflow",
+            "type": "boolean",
+            "default": false
+        },
         "sizeup": {
             "$ref": "https://raw.githubusercontent.com/lerebear/sizeup/main/src/config/schema.json"
         }
diff --git a/dist/index.js b/dist/index.js
index df21989..6d31d14 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -16492,7 +16492,7 @@ const COMMENT_METADATA = '<!-- data key="id" value=score-threshold-exceeded-comm
  * @param score The score the pull request received from `sizeup`
  * @param config The configuration for this workflow run
  */
-async function addOrUpdateScoreThresholdExceededComment(pull, score, config) {
+async function addOrUpdateScoreThresholdExceededComment(pull, score, optInStatus, config) {
     const threshold = (0, initializer_1.configOrDefault)(config.commenting?.scoreThreshold, DEFAULT_SCORE_THRESHOLD);
     if (score.result <= threshold)
         return;
@@ -16501,6 +16501,10 @@ async function addOrUpdateScoreThresholdExceededComment(pull, score, config) {
         core.info('Skipping commenting on a draft pull request');
         return;
     }
+    if (optInStatus === initializer_1.OptInStatus.Shadow) {
+        core.info('Skipping commenting because this workflow is running in shadow mode');
+        return;
+    }
     const comment = scoreThresholdExceededComment(pull, score, config);
     if (!(0, initializer_1.configOrDefault)(config.commenting?.addCommentWhenScoreThresholdHasBeenExceeded, true)) {
         const indentedComment = comment
@@ -16685,7 +16689,7 @@ var __importStar = (this && this.__importStar) || function (mod) {
     return result;
 };
 Object.defineProperty(exports, "__esModule", ({ value: true }));
-exports.configOrDefault = exports.pullRequestAuthorHasNotOptedIn = exports.loadConfiguration = void 0;
+exports.configOrDefault = exports.getOptInStatus = exports.OptInStatus = exports.loadConfiguration = void 0;
 const core = __importStar(__nccwpck_require__(2186));
 const fs = __importStar(__nccwpck_require__(7147));
 const path = __importStar(__nccwpck_require__(1017));
@@ -16708,25 +16712,36 @@ function loadConfiguration() {
     return YAML.parse(fs.readFileSync(configFile, 'utf8'));
 }
 exports.loadConfiguration = loadConfiguration;
+var OptInStatus;
+(function (OptInStatus) {
+    OptInStatus[OptInStatus["In"] = 1] = "In";
+    OptInStatus[OptInStatus["Out"] = 2] = "Out";
+    OptInStatus[OptInStatus["Shadow"] = 3] = "Shadow"; // The user has opted out but we're running in shadow mode so we should continue silently.
+})(OptInStatus || (exports.OptInStatus = OptInStatus = {}));
 /**
  *
  * @param pull The pull request that triggered this workflow
  * @param config The configuration for this workflow
- * @returns True if the pull request author has not opted into this workflow
- *   (meaning that we should quit early), false otherwise (meaning that we
- *   should proceed with evaluation of the pull request).
+ * @returns A status indicating how to continue running the rest of the workflow.
  */
-function pullRequestAuthorHasNotOptedIn(pull, config) {
+function getOptInStatus(pull, config) {
     const usersWhoHaveOptedin = config.optIns || [];
-    if (usersWhoHaveOptedin.length &&
-        !usersWhoHaveOptedin.find((login) => login === pull.user.login)) {
+    const userHasOptedOut = usersWhoHaveOptedin.length &&
+        !usersWhoHaveOptedin.find((login) => login === pull.user.login);
+    if (userHasOptedOut && config.shadowOptOuts) {
+        core.info('Executing workflow silently for user who was not opted in');
+        return OptInStatus.Shadow;
+    }
+    else if (userHasOptedOut) {
         core.info(`Skipping evaluation because pull request author @${pull.user.login} has not opted` +
             ' into this workflow');
-        return true;
+        return OptInStatus.Out;
+    }
+    else {
+        return OptInStatus.In;
     }
-    return false;
 }
-exports.pullRequestAuthorHasNotOptedIn = pullRequestAuthorHasNotOptedIn;
+exports.getOptInStatus = getOptInStatus;
 /**
  * If necessary, provides a default for an undefined configuration value.
  *
@@ -16798,12 +16813,13 @@ async function run() {
         const git = new git_1.Git();
         await git.clone(pullRequest.base.repo.full_name, pullRequest.head.ref);
         const config = (0, initializer_1.loadConfiguration)();
-        if ((0, initializer_1.pullRequestAuthorHasNotOptedIn)(pullRequest, config))
+        const optInStatus = (0, initializer_1.getOptInStatus)(pullRequest, config);
+        if (optInStatus === initializer_1.OptInStatus.Out)
             return;
         const diff = await git.diff(pullRequest.base.ref);
         const score = await evaluatePullRequest(pullRequest, diff, config);
-        await applyCategoryLabel(pullRequest, score, config);
-        await (0, commenting_1.addOrUpdateScoreThresholdExceededComment)(pullRequest, score, config);
+        await applyCategoryLabel(pullRequest, score, optInStatus, config);
+        await (0, commenting_1.addOrUpdateScoreThresholdExceededComment)(pullRequest, score, optInStatus, config);
     }
     catch (error) {
         if (error instanceof Error)
@@ -16848,7 +16864,7 @@ async function evaluatePullRequest(pull, diff, config) {
  * @param score The score the pull request received from `sizeup`
  * @param config The configuration for this workflow run
  */
-async function applyCategoryLabel(pull, score, config) {
+async function applyCategoryLabel(pull, score, optInStatus, config) {
     if (!score.category?.label) {
         core.info('Skipping labeling because no category label was provided');
         return;
@@ -16858,6 +16874,10 @@ async function applyCategoryLabel(pull, score, config) {
         core.info('Skipping labeling of a draft pull request');
         return;
     }
+    if (optInStatus === initializer_1.OptInStatus.Shadow) {
+        core.info('Skipping labeling because this workflow is running in shadow mode');
+        return;
+    }
     await ensureLabelExists(pull, score, config);
     await applyLabel(pull, score, config);
 }
diff --git a/src/commenting.ts b/src/commenting.ts
index 2cbbf94..6a645a4 100644
--- a/src/commenting.ts
+++ b/src/commenting.ts
@@ -3,7 +3,7 @@ import * as github from '@actions/github'
 import { PullRequest } from '@octokit/webhooks-types' // eslint-disable-line import/no-unresolved
 import { Score } from 'sizeup-core'
 import { Configuration } from './configuration'
-import { configOrDefault } from './initializer'
+import { OptInStatus, configOrDefault } from './initializer'
 
 const DEFAULT_COMMENT_TEMPLATE = `
 👋 @{{author}} this pull request exceeds the configured reviewability score threshold of {{threshold}}. Your actual score was {{score}}.
@@ -28,6 +28,7 @@ const COMMENT_METADATA =
 export async function addOrUpdateScoreThresholdExceededComment(
   pull: PullRequest,
   score: Score,
+  optInStatus: OptInStatus,
   config: Configuration
 ): Promise<void> {
   const threshold = configOrDefault(
@@ -44,6 +45,13 @@ export async function addOrUpdateScoreThresholdExceededComment(
     return
   }
 
+  if (optInStatus === OptInStatus.Shadow) {
+    core.info(
+      'Skipping commenting because this workflow is running in shadow mode'
+    )
+    return
+  }
+
   const comment = scoreThresholdExceededComment(pull, score, config)
 
   if (
diff --git a/src/config/schema.json b/src/config/schema.json
index 1b5221e..49c1d38 100644
--- a/src/config/schema.json
+++ b/src/config/schema.json
@@ -59,6 +59,11 @@
                 "type": "string"
             }
         },
+        "shadowOptOuts": {
+            "description": "Whether or not to compute a score even for users who have opted out of the workflow",
+            "type": "boolean",
+            "default": false
+        },
         "sizeup": {
             "$ref": "https://raw.githubusercontent.com/lerebear/sizeup/main/src/config/schema.json"
         }
diff --git a/src/configuration.ts b/src/configuration.ts
index df9af9c..7288f7e 100644
--- a/src/configuration.ts
+++ b/src/configuration.ts
@@ -51,7 +51,11 @@ export interface Configuration {
    *
    * @minItems 1
    */
-  optIns?: string[]
+  optIns?: [string, ...string[]]
+  /**
+   * Whether or not to compute a score even for users who have opted out of the workflow
+   */
+  shadowOptOuts?: boolean
   sizeup?: Configuration1
 }
 /**
@@ -63,33 +67,62 @@ export interface Configuration1 {
    *
    * @minItems 1
    */
-  categories?: {
-    /**
-     * human-friendly name of the category
-     */
-    name: string
-    /**
-     * A visual label that should be used to represent this category
-     */
-    label?: {
+  categories?: [
+    {
       /**
-       * name of the label that should be used to represent this category
+       * human-friendly name of the category
        */
       name: string
       /**
-       * describes the meaning of the label that will be used to represent this category
+       * A visual label that should be used to represent this category
        */
-      description?: string
+      label?: {
+        /**
+         * name of the label that should be used to represent this category
+         */
+        name: string
+        /**
+         * describes the meaning of the label that will be used to represent this category
+         */
+        description?: string
+        /**
+         * preferred CSS hex color label that should be used to represent this category
+         */
+        color?: string
+      }
       /**
-       * preferred CSS hex color label that should be used to represent this category
+       * inclusive upper bound on the score that a pull request must have to be assigned this category
        */
-      color?: string
-    }
-    /**
-     * inclusive upper bound on the score that a pull request must have to be assigned this category
-     */
-    lte?: number
-  }[]
+      lte?: number
+    },
+    ...{
+      /**
+       * human-friendly name of the category
+       */
+      name: string
+      /**
+       * A visual label that should be used to represent this category
+       */
+      label?: {
+        /**
+         * name of the label that should be used to represent this category
+         */
+        name: string
+        /**
+         * describes the meaning of the label that will be used to represent this category
+         */
+        description?: string
+        /**
+         * preferred CSS hex color label that should be used to represent this category
+         */
+        color?: string
+      }
+      /**
+       * inclusive upper bound on the score that a pull request must have to be assigned this category
+       */
+      lte?: number
+    }[]
+  ]
   scoring?: {
     /**
      * an expression, written in prefix-notation, that describes how to combine features to produce a score
@@ -99,6 +132,10 @@ export interface Configuration1 {
      * named expression aliases, each of which can be used as shortand in a formula
      */
     aliases?: {
+      /**
+       * This interface was referenced by `undefined`'s JSON-Schema definition
+       * via the `patternProperty` "^[\w][\w-]*$".
+       */
       [k: string]: string
     }
   }
diff --git a/src/initializer.ts b/src/initializer.ts
index 007f895..9a751e9 100644
--- a/src/initializer.ts
+++ b/src/initializer.ts
@@ -24,32 +24,39 @@ export function loadConfiguration(): Configuration {
   return YAML.parse(fs.readFileSync(configFile, 'utf8')) as Configuration
 }
 
+export enum OptInStatus {
+  In = 1, // The user has opted into the full behaviour of this workflow.
+  Out, // The user has opted out of the workflow, so it should be aborted.
+  Shadow // The user has opted out but we're running in shadow mode so we should continue silently.
+}
+
 /**
  *
  * @param pull The pull request that triggered this workflow
  * @param config The configuration for this workflow
- * @returns True if the pull request author has not opted into this workflow
- *   (meaning that we should quit early), false otherwise (meaning that we
- *   should proceed with evaluation of the pull request).
+ * @returns A status indicating how to continue running the rest of the workflow.
  */
-export function pullRequestAuthorHasNotOptedIn(
+export function getOptInStatus(
   pull: PullRequest,
   config: Configuration
-): boolean {
+): OptInStatus {
   const usersWhoHaveOptedin = config.optIns || []
-
-  if (
+  const userHasOptedOut =
     usersWhoHaveOptedin.length &&
     !usersWhoHaveOptedin.find((login: string) => login === pull.user.login)
-  ) {
+
+  if (userHasOptedOut && config.shadowOptOuts) {
+    core.info('Executing workflow silently for user who was not opted in')
+    return OptInStatus.Shadow
+  } else if (userHasOptedOut) {
     core.info(
       `Skipping evaluation because pull request author @${pull.user.login} has not opted` +
         ' into this workflow'
     )
-    return true
+    return OptInStatus.Out
+  } else {
+    return OptInStatus.In
   }
-
-  return false
 }
 
 /**
diff --git a/src/main.ts b/src/main.ts
index eca889e..96c7b4d 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -9,7 +9,8 @@ import { Configuration } from './configuration'
 import {
   configOrDefault,
   loadConfiguration,
-  pullRequestAuthorHasNotOptedIn
+  getOptInStatus,
+  OptInStatus
 } from './initializer'
 import { Git } from './git'
 import { addOrUpdateScoreThresholdExceededComment } from './commenting'
@@ -37,12 +38,18 @@ export async function run(): Promise<void> {
     await git.clone(pullRequest.base.repo.full_name, pullRequest.head.ref)
 
     const config = loadConfiguration()
-    if (pullRequestAuthorHasNotOptedIn(pullRequest, config)) return
+    const optInStatus = getOptInStatus(pullRequest, config)
+    if (optInStatus === OptInStatus.Out) return
 
     const diff = await git.diff(pullRequest.base.ref)
     const score = await evaluatePullRequest(pullRequest, diff, config)
-    await applyCategoryLabel(pullRequest, score, config)
-    await addOrUpdateScoreThresholdExceededComment(pullRequest, score, config)
+    await applyCategoryLabel(pullRequest, score, optInStatus, config)
+    await addOrUpdateScoreThresholdExceededComment(
+      pullRequest,
+      score,
+      optInStatus,
+      config
+    )
   } catch (error) {
     if (error instanceof Error) core.setFailed(error.message)
   }
@@ -102,6 +109,7 @@ async function evaluatePullRequest(
 async function applyCategoryLabel(
   pull: PullRequest,
   score: Score,
+  optInStatus: OptInStatus,
   config: Configuration
 ): Promise<void> {
   if (!score.category?.label) {
@@ -117,6 +125,13 @@ async function applyCategoryLabel(
     return
   }
 
+  if (optInStatus === OptInStatus.Shadow) {
+    core.info(
+      'Skipping labeling because this workflow is running in shadow mode'
+    )
+    return
+  }
+
   await ensureLabelExists(pull, score, config)
   await applyLabel(pull, score, config)
 }