Are you getting personal emails or are you getting PM's? If you don't want either when there is another reply to a Thread you've replied to, then in Settings, make sure <label for="sel_autosubscribe">Default Thread Subscription Mode:</label> says Do Not Subscribe. Then, if you ever want to 'watch' a thread, you have to go above the thread you are looking at and in Thread Tools, choose Subscribe to this Thread. When you no longer want to 'watch' the thread, you have to Unsubscribe.