Good point. (last one) I agree.
As far as those "uninteresting" threads, it seems to be a moot point to me to clear them. If it's a relatively new thread, chances are there will be new posts to it the next time I return. Thus, it would have been time wasted to open it just to clear it for next time, when it won't be cleared. I could be "clearing" it for days if others find it interesting.
Theoretically, the only time clearing an "uninteresting" thread is not a waste of my time would be after the final post has been made to it. However, since I am not clairvoyant, I don't know when that would be.
I do not make a habit of opening threads and not reading them. Nor do I use the "Mark all read" button we've been discussing. I also do not notice unopened threads that I've ignored piling up on the forum lists. Somehow, they manage to clear themselves.