As far as I know, the message from root saying you got a reply stays in the top of your chatterbox nodelet until you manually delete it.
I see replies all the time to nodes other than the OP. For instance Rhys, you should get a message because of this post, if you have /msg me turned on.
So I think /msg me works well, as long as all you are interested in is replies specifically to your node.
But I think a point can be made for having a count of replies, to any node in the thread, which I think is what HelgeG wants. I have made posts in threads where I either asked an additional question that doesn't get answered right away, or it's a thread I would just like to know if more has been added. If the forthcoming replies don't come for weeks, well, it's going to be tough going back through my list of Nodes I Wrote to manually check for replies, especially as the list gets longer.
Being able handle replies to any post in a thread could be hard to implement, though, I don't know.
Another problem arises, however. Just having a count of replies means I need to make a mental note of how many replies a thread has, so when I go back later to look, I can see if it's higher. That's another tough thing to do with a long list of Nodes I Wrote. Or even a short list, for those of us who suffer from CRS1. The way to solve that would be to be able to reset the count. More complexity that's probably hard to implement.
I think it's a good idea, not sure if pmdev would do it; but it never hurts to ask ;)
Although I recently found out that any one of us can write code for our own use (and to share) that can access the PM data in various ways. Maybe this is something that can be accomplished that way.
1Can't Remember Shit