mstdn.jp went down and the user count dropped by 42k. https://mastodon.social/media/qqkgZWYamblDKbqNWCE
Also, the instance did eventually come back up, but it looks like the old users/statuses haven't been restored. https://mastodon.social/media/aCplfi3mURfsE6Rsms0
Your graph is interesting if you think about it. Since #mastodon users cannot be natively deleted- the only time you'd register a user count drop is when a server instance dies. 🔌 @cs