I refer to:
How to handle these situations? Myself and one other user, have posted an answer on his question and instead of upvoting or accepting an answer, I have a comment on my answer saying "Thanks, that's all I needed" and then they delete the question.
I voted to undelete it, and I think it got undeleted once, but then OP deleted it again immediately.
I'm not able to comment on the question explaining how it's not how the site is intended to be used, because I get an error about comments on deleted questions can't be submitted or something like that.