OK, I don't know if this would be possible, but here it goes...
When someone starts a new topic, by hitting the "submit new topic" button maybe that could trigger a search of just the topic names, in that forum (instead of all the replys, and all forums) and come up with possible topics already covering the newly submitted one. It could say something like "We have found a few topic titles that may be discussing your topic already. Please take a moment to look at these and ensure that yours is not a repeat."
If this could be done, repeat topics would be virtually eliminated.
-------------
"X" marks the spot in 2001!