Something like this was proposed a while back, japhy, and it sounded good to me. If I remember right, the request was for a "jump to top of thread" link on each and every reply node, but that it would add humongously to box utilization (and to response times), so was shot down.
in reply to threaded discussion maybe?
I'm no DB guru, but suspect your idea might have the same show-stopping drawback. If I'm wrong, doubtless some fine Monk will set the record straight. 8^) If I can dig up the thread, I'll add an Update: