I am currently moderating for another forum, what we do is we edit the content by moving his original content into a secured thread that only moderators can access, then we put in a warning message in his posting asking the poster to contact the our Administrator for approval. Failing which, we will remove the thread and block the ID and IP.
The approval process is pretty tedious, we will meet up with the poster (during TT or special arrangement) and examine their items for QC (quality check) purposes to make sure those items can pakai. Of course some back ground check through conversation, we will try to gather or discover if there's ill intention in between..
We do all this just to make sure non of our members get cheated or con by errant traders. Plenty of them out there.
The moderators have a duty to make sure a save "playing ground" for their members.