It's really bugging me, and I think that something needs to be done about it, I keep on finding questions like this one which have very good answers, and some of the answers have a lot of upvotes, and clearly answer the question, however, as the OP's account has been deleted, these questions will always stay in the unanswered state, which really bugs me. So I would propose that something be done about this, for instance if all the mods got together and did a vote on which of the answers they think is most helpful (if any), and then the one that they believe will help others most, to be marked that as accepted. Because it's not about the OP any more as they no longer have an account, it's about what will most likely solve other people's problems. Or I think that at least something should be done about them because currently it is impossible for any answer to be accepted, even if it perfectly answers the question.
The voting system already does this.
The most popular answer floats to the top. Whether or not it has been accepted really makes very little difference to the person who finds the answer via a search engine. They only care that they see the best answer first. Which is what happens most of the time.