I think most of these are third party metrics collected from ad services, we’ve seen a few choice ones from reddit about how little traffic has dropped but of course Reddit will find ways to express an ever rising metric until they can’t.

Facebook somehow reports near magical user growth, but 90% of the people I’m connected to it barely seem to be there.

I strongly suspect, but can’t prove, that the 80/20 rule applies to reddit. I expect 20% of the users create 80% of the content and engagement, and that even if only 1% of reddit leaves it’s almost certainly coming out of the productive 20%. However i’ll bet Reddit will never start openly sharing stats about how engaged the top quintile of their users are, because that provides too much insight. Much better to talk about monthly active users and count those of us that flip over there by mistake or for one community we can’t replace here.