I'm wondering how difficult it would be to keep an "audit trail" of posts, i.e. archive the entire message when it's first posted, but then keep a record of any changes. That would allow users to edit posts as they wished, but if there any question of impropriety, would allow the admins to retrace what was said, and take appropriate action.
Some message board software can do that, dunno (obviously) about this one.
Not sure that this is a good idea, unless you can read the state of mind of the poster. Sometimes people say things in the heat of the moment, or just carelessly....
-R