A while ago I saw a feature on a forum that I like to see in UBB.threads. It's a possibility for moderators and admins to make a comment in/under a "wrong" post. The user can not delete/edit that moderator comment, but is able to edit the post. In that way you can correct a users post without editing the post itself. Maybe you can even email/pt that user so you're sure that the user will read it.
