If you were caught up when you left, yes. If you start reading a long thread and leave in the middle, you don't want to jump to the first new post since you left when you come back.

I'd love to see a button that takes me straight to that list, except not even bothering to show topics without new posts (or bookmarks in the middle). Especially on my phone.

Except if I stopped reading the thread ages ago, I don't want to see it at the top. The more I read the ones I do want to keep caught up on, the more the ones I don't care about any more stand out with their green counts when I sort by most recent activity. And I don't necessarily want to have to drain them, so that's no solution either.

I just want a list of the ones I've been reading that have new posts. What is so difficult to understand about that?

Hide idle is brilliant! Perfect! Thanks!!!

I think he means how when you turn Hide Idle on, click a thread, then back up to the list, turning it off does nothing until you refresh or click sort again.