Ah. I'm guessing that this instance has now made the same change as programming.dev - counting 'active users' as people who post, comment or vote, not just those who post or comment.
Stats will be a bit crazy for a few days, as the 7-day average will include the massive 1-day increases (e.g. !redhead@lemmynsfw.com went from 46 active users to 1569) but they'll normalise from about the 12th December.
EDIT: Issue is fixed now, thank you.
~~I'm not sure anything from this instance is federating anywhere since this change.~~
~~Looking at activitypub, attempting to subscribe to something gets no reply (the screenshot below shows me trying with 3 different communities, followed by what's expected to happen with a random community on another 0.19 instance)~~
~~Looking at an active community (like nuclear@feddit.nl), there's been 6 posts in the past 2 days that aren't showing up anywhere else (at <whatever_instance>/c/nuclear@feddit.nl)~~