I just found that my own answer to my own question has been marked as accepted today, and I got +5 rep for it. I didn't do this, and I didn't think it was possible to get rep for accepting your own answer anyhow. Did some moderator do this, or is this a bug?
You didn't get +5 for the accept - that was just an unrelated upvote today. The answer was accepted by you yourself back on Apr 10 '16 four minutes after you wrote it, as can be seen from the timeline.