My question is related to Do moderators see the previous versions of edited comments? and Moderators should see the post as I flagged it, not the edited version. The accepted answer on the latter proposes to mark a flag as disputed if a post has been edited, which is not what I am after.
My question originates from this meta post on Seasoned Advice meta: Has anybody else received abusive comments that were later edited or deleted? In this case, a user is posting abusive comments which are edited or deleted within the grace period. As indicated, moderators can't see the original version of a comment, which hinders their ability to make a good judgement of things and ban an user for this, since there is no evidence.
It seems wrong that a moderator should ask for screenshots from the community in order to do their work…
Therefore, I suggest to add the original message to the flag. This can just be a field in the flag table, which contains the original message. This will give moderators the ability to do their work, and prevent abuse by users.