Wow, I’m surprised I only just noticed this.
I think collapsing it into a “# replies” notification where you’d still be able to get to all the individual notifications would be good. Or maybe a combo notification where the main link takes you to the earliest unread reply from the group, but I small icon takes you to the whole notification group. 
That would also solve the problem where you get replies in the same topic from multiple people, and it’s sometimes hard to find the later replies to you in the jumble of replies.