Well for 1 I don't think that the OP get any reputation from accepting his own answer as opposed to someone ease's answer(at I'd hope not, it's a bad incentive).
It's a mean thing to do, it's essentially telling you that your answer's not good enough to deserve to be marked, but there's really not too terribly much you can do about it. he's free to determine the answer to his own question.
And after a cursory look, his answer looks a little bit different from yours(it's longer for 1)., and if he believes it to be substantially better, than he's within his rights to mark his own as the answer. A lot of the point of the marked answer is for people who come here googling the problem, not for the glory of the answerer.
I have answered my own questions before, but ONLY if nobody else has provided a correct answer at the point where I have gone ahead and found my answer.