I posted an answer at Does the following series converge?, then noticed it was wrong, deleted it, edited it, and undeleted it. (The system asks whether I want to "vote to undelete", which is a bit confusing, since I simply want to undelete and the answer does in fact get undeleted immediately without awaiting further "votes", but that's a different problem.)
After that, I noticed that the page is now saying "1 answer", though there are two answers, one that had been there before I'd posted mine, and my undeleted answer. I logged out to check whether this was maybe just an artefact of how it was presented to me as the author/deleter/undeleter of the answer, but after logging out and reloading the page it was still showing two answers but saying "1 answer".