Came here to say this as well. As funny as this would be if it were an accident, just prior to me going scorched earth on my accounts I saw several subreddits in protest that made everyone subscribed to their sub a mod, and confirmed it myself.

It's very likely a subreddit that the person was subbed to and forgot/didn't know they were doing that.

If I read the announcement correctly, that is implemented by a bot with mod privileges that parses comments and takes actions on users' behalf. I don't think it's practical to literally make every user a moderator.

On r/politicalhumor and r/madlads, the answer is yes. But you need subreddit karma to log mod actions. There is a bot running in those subs which facilitates it.