I'm sure this suggestion will get lost and perhaps it's only me that it would be useful for, but anyway...
In my watchlist, I get the little number symbol at the side of each watched thread, to let me know how many new responses there have been since I was in the thread. I think this is useful and I like the feature.
What would be even more useful is an ability to 'Mark as Read', so the notification clears. It's a bit of an admittedly minor faff to open the thread and come back out of it, just to clear the notification. Sometimes, for instance, there's only been one response, which I can see from the watch page and opening it is unnecessary, or maybe some other reason that I don't want/need to open that thread right away but I don't want the clutter of a load of notifications.