I don't know if this is a bug or a feature, or even a priority... I originally had the email notifications for watched threads turned on by default. It got to the point where it was flooding my inbox and was redundant with my attention to the alerts in the browser, so I turned it off. What happened was the changed setting only went into effect for new watched threads. I still continued to receive email notifications for threads I was already watching. The only way I could stop it was to manually unwatch then rewatch each specific thread. Again, I don't know if it works like that on purpose for some reason, but personally I would like it if preference changes of that sort were applied to everything, not just new items.