I certainly don't have many conversations going at once but I posted this question, got busy at work, then got on a flight and totally forgot until today. I missed tons of interesting comments, I would have loved to reply to. If I had gotten some sort of notification, it would have been cool for me.

I think it can be done very minimally, like someone suggested, just adding a number next to the threads link "threads (12)". I feel like the website isn't bothering you too much in that case.