I have an instructor who says a student is repeatedly posting inappropriate content in a Discussion Board, even after the instructor has given guidance as to appropriate posting.  Currently, the only way to control this is for the instructor to go in and delete the offending messages, but by that time, the rest of the students may have seen it.

There should be a way for an instructor to set the discussion so that it must be moderated (posts don't appear to the students until the Teacher/TA has approved them) or that a particular student can be blocked from the discussion.