There's actually code to stop duplicates in two places. The only way around it is to make minor changes and re-submit.
He must have been using "Create Conversation" as a preview, and then using the browser's back button to go back to the "Create Conversation" page and edit things.
This guy keeps on posting the same ad (maybe he fell asleep on the keyboard):
http://www.lfgss.com/conversations/256657
http://www.lfgss.com/conversations/256655
http://www.lfgss.com/conversations/256654
http://www.lfgss.com/conversations/256652
http://www.lfgss.com/conversations/256651
http://www.lfgss.com/conversations/256650