Is it better to not accept any answer or reply to your own question (maybe stating that the question appears unanswerable) and accept that one?
EDIT: another way to look at this question: is accept rate commonly considered an indicator of the "quality" of questions? If it is so, then answering and accepting your answer is kind of like cheating the system.
Of course you should do your best to make your question as clear as possibile, but sometimes you just don't get what you want maybe because the question didn't raise much interest and slipped over or because it doesn't really have one fully satisfying answer. From another point of view, the questions more easily answered are those of less value (i.e. if the answer is easy you might as well find it yourself) and are probably the most repeated ones.
Well, just a thought about accept rate and those ugly red lines in your profile.