Snarkpit has a version of this: when someone asks a question, they can choose to mark a post as a corect answer...prevents threads going on longer than necessary, and lets people quickly find what the correct answer was. I think this could be useful here.
I dunno exactly what a full implementation would entail, but surely the most basic functionality - allowing posters to mark their post as a question, then giving them a "issue resolved" button in the thread - wouldnt be terribly hard?