The purpose of this document is to capture all the conventions in the project. For example, all files that act as living documentation should state their purpose at the top under the heading. Just like this one does.
The guiding principle is to be as transparent as possible. Thus, initialism and acronyms should be avoided at all reasonable cost. This may result in longer names but is easy for anyone new to the project to understand. It also helps reduce cognitive load and produce self documenting code.
That said there are, of course, exceptions. One might be an initialism or acronym leaking in from a third party library. In this case or if it is otherwise unwieldy to avoid then it can be used.
Functions should endeavor to be as declarative in their purpose as possible.