improvement: what to document

https://gitlab.gwdg.de/fe/technical-reference/-/blob/master/chapters/documentation.md#general-notions-about-documentation

Don't document a language's specifics, e.g. operators.
Example: Use of => in the XQuery expression replace("qbc", "q", "b") => substring(1, 2) MUST NOT be explained in a comment.

add: except you are using a feature that is

• deprecated
• legacy
• undocumented
• a breaking change compared to a previous version that is still being actively maintained