I see this weird thing from time to time that I don’t think I’ve seen mentioned, but some certain unread threads can get sort of stickied just below pinned threads and don’t seem to go away as long as they’re on the first forum page. It seems to generally be some thread with 0 replies, maybe also locked, and it gets placed properly when I open it and it then has no unread posts. I do have the app set to show unread posts first, but these are threads I’ve never visited.
One particular, current example from SH/SC:
This “Measuring Viscosity...” thread:
I’m gonna open the thread and see what’s in it and report back/edit this post.
e: 0 replies but unlocked. Marking it as unread does not cause it to go back to the top of the thread list, it stays where it was in its read state.
— fourwood