re: birdsite
I've got mixed feelings too. On a usability side, there's not many other ways to comment on another post. The whole "last retweet" thing is actually in practice pretty useless; it's often near-impossible to figure out which tweet is actually being referenced. At least in some clients--maybe the Twitter web client is different.
That said, I don't believe that you need to be notified about the quote, and especially not the /content/ of it. :-/