Not quite. Since most people suggesting prior suggested elements do not use the search bar, why not do it for them? Basically, when creating a new topic in the feedback subforum, just before the thread is posted a keyword search is automatically initiated, if one or more threads with enough matching keywords are found, it will ask the user if they are sure they want to post and then show them the pre-existing threads, that way people cannot plead ignorance.
This thread is edging pretty close to the territory I made this thread to warn about. :
The chances of some automatic, magic way to prevent people from posting redundant suggestions are probably very slim. It's just a warning that if I catch anyone obviously flaming or lingering around and not being helpful in suggestions, bans will probably follow.
I will have to agree with @Catelite. The flames have to be extinguished. I have caught myself getting mad at the newer people myself who are suggesting previously suggested and rejected things before. I will try if someone hasn't done it already to lead the people who do suggest in that way to lead them in the right direction.
Except that adding layers between a person and producing a post could not only produce false hits, but annoy people and deter them from posting in the first place?