Typical MK3 owners, slow on the uptake
Seriously though what about a message in the content field of the 'post new topic' saying something like "Have you used the search function above? Please do so before before posting a new topic which may have been covered previously"
This will force people to read and delete it because it is in the content field.
iirc that *should* only be a quick edit of 1 of the html/php files that controls the posting of new topics.

that coupled with this sort of mod would probably work really well.
That or mods just need to be more ruthless and start messaging people, locking posts and pointing to a topic with the answers.
This is also why a wiki would be awesome.