Is there a reason that Recently Active Threads is not sufficient for the purpose?

Well, Recently Active Threads is a handy resource and I do use it, but it's not quite the same thing. The obvious difference is the common one between push and pull UIs.

Incidentally tracking replies to nodes is not as easy as it sounds. Theres a lot of subtle issues associated to it that arent so easy to resolve.

Indeed, I hope not to have conveyed the impression I thought it to be different. I can imagine full well that it wouldn't be an easy task. I was just wondering wether there were any ongoing project in that direction...

BTW: nice .sig!