I'm pretty sure this is only visible on c/196 right now because it's grown to the point where there's a new post every 5-15 minutes.
Hours apart, I'll log on and see the same content on Activate/Hot ranking. I'm still seeing stuff from 24-48 hours ago in the first page, which is wildly different behavior than a comparable subreddit where you'd barely see the last 12 hours on the first few pages.
Can this be fine-tuned per instance or per community?
I don't think old posts are changing rank anymore. It's like every post pre-update is frozen at the activity score it last had.
That's what I'm thinking happened, my front page looks identical when I sort by hot/active