I just noticed that Community ♦ deleted this question, probably the same time the asker deleted his account (I can see a User was removed for the same timestamp in my rep log). I've seen why does community user delete answers on close of question?, but I don't understand why it happened in this case.
The account got nuked along with all its posts (another deleted question and yet another one) which is weird, as he got some upvoted questions with upvoted answers which were not closed. Obvious loss of good content.
I know spammers eventually meet this fate by the hand of moderators, so maybe that user started to spam (or got his account hacked and used for spam) and moderator didn't notice it has valid posts as well.
Until official response will come, that's my best guess and $0.02.