This may have been asked before, but I can't find it searching. If this has been brought up before, point it out please.
This is also not commonly a problem, but on occasion, one pops up. The "problem" is that new users add an answer to a question that already has an accepted answer (example). I'm only concerned about questions that are quite old, say at least 3 months old.
The question goes straight back to the top of the front page, but has already been thoroughly discussed and answered. The new "answer" is commonly of no value to the question, and the answer previously provided has already been implemented.
I'm essentially proposing that you need a certain rep (maybe 15, even just a registered account) to be able to post an answer to a question with an accepted answer that is so old (say
3 months 1 year or older).