I'm also not a fan of this change. Perhaps I'm missing something, but in the past it appeared to recognize when I last visited a forum and, next time, only showed threads with new posts since that date/time. Regardless of whether I read them or not.
Now, it seems to show all threads with new posts since I read the thread. So if I never read the thread, it's always bolded.
In the past, if I wasn't interested in a thread, it would stop appearing when posting to it stopped. Now it appears that it will remain as bold forever.
To get back to the old treatment, I have to actively "Mark this Forum Read" every time before exiting.
I'd very, very much like to have the old option back. I prefer not to have to actively look at the title and disregard a thread over and over, forever. Or go into it just to make it go away. Or take an action that I never had to before.
This is like a USAirways Dividend Miles program enhancement.