Add the ability to lock down the comments section

[violine1101]

Request from @MikeUnverferth

The Problem

On some bug reports with high popularity, we often get only irrelevant comments with only complaints or me-too's. If a notice is added to the description or to the comments section stating that new comments should be on topic, that often ends up being ignored.

Thus, it might be useful to put the bug report into a mode where all new comments first have to be approved by a moderator.

Possible Solution

By adding a restricted comment like ARISA_LOCK_COMMENTS, Arisa would first post the following notice (or something similar):

All new comments on this ticket require moderator approval before being posted.
Please only add a comment if you have new information related to reproducing or potentially working around this issue.

Then, if such a moderator ARISA_LOCK_COMMENTS directive exists, Arisa will automatically set any new incoming comments by regular users to helper+. The moderator who locked the comments section then should watch the ticket and manually change the visibility of comments when needed.

[MikeUnverferth]

Arisa should put the notice at the beginning of the Description instead of adding as a comment so it will remain visible after some comments become unhidden.

[osfanbuff63]

Arisa should put the notice at the beginning of the Description instead of adding as a comment so it will remain visible after some comments become unhidden.

IMO it should post essentially a sticky comment so it's always at the bottom of the comments, as well as in the description maybe?