[Brendinooo]

>don't all RSS readers do this when you "Sort by time descending?"

Liferea doesn't! At least not that I can tell. It will do this with unread items but then disappear. There's no option that's just "get all of the feed data, throw it in one place, and sort chronologically".

>I simply mark them as read

I don't want to mark them as read! I don't do this with social media posts. The nice thing about this is that, if things build up, I don't have to feel like I've fallen behind.