I belong to a lot of forums and I've never seen this type of notification before. I don't want to be notified if someone quotes me. What's worse, though, is that two email notifications appear to be generated when someone replies to you in a subscribed thread and (as is common practice) they happen to quote you.
I don't see anything in the settings to disable 'you've been quoted' notifications. Am I missing something, or does this need to be disabled system-wide? Seems to me that at the very least, two notifications should never be sent out as the result of a single post.