I think that would underscore that what appears to be a conversation between two people is not. That's important and I think often lost in online discussion. If UserX doesn't reply they might have been persuaded to UserY's position and one way of signaling that is to not reply. Meanwhile there's very likely someone who will read a well reasoned and backed up comment and nonetheless disagree, and they're most likely to reply given their disagreement. More so in the age of bots. The aggregate effect is for discussions to be weighted harshly negatively to the point of destructively.
Edit-I'm not very aware of the "famous user" effect. Sure there are usernames I recognize, but it's few, and the UI doesn't seem to give them much weight. I 'worry' more about the criticality of the site.