I think trolls are coming to ancient posts because they don't expect us to notice. Another possible explanation is these people simply don't understand that the posts are old as hell, and decide to throw in their two cents.

regardless, pretty much all of it I've seen is people from other instances (most common I've seen is lemmy.world) who have something contrarian to say. Some weird shit.

I do the same, and it's been happening a lot lately! I think maybe people are seeing our communities, and just digging back in old posts without realizing how old they are. Once one person comments, it bumps into "hot" and everyone piles in.

Or it's a Lemmy bug? It's very strange!