Try the action's token

.github/workflows/token_issue.yml

@@ -0,0 +1,15 @@
+name: Token issue debugging
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  debugging:
+    runs-on: ubuntu-latest
+    permissions: write-all
+    steps:
+    - name: Write a comment on a PR
+      run: |
+        curl -LsX POST -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" -d '{"body":"Hello :)"}' "${{ github.event.pull_request.comments_url }}"
+        echo $?