Okay, this is the other exception which I realized later. However, I have marked several threads as “tracked” (because I’m interested in them or I read the thread for 4 minutes after which they are automatically marked). Of course I wouldn’t get a reply directly to me if I never made a post there, or maybe I am just interested in other posts as well that are not replies to me.
The only way I currently see whether my tracking discussions have new posts is when I get the digest email and would like to read on on a specific thread. And then I still have to go back to the topic list page to be able to see “Unread (N)”.