As a starting point, I'd be satisfied with getting this feature proposal implemented, and just having a norm that says that every comment that presents a contrary argument should have either an explicit reply or a disagreement status indicator set by the author of the parent of that comment, with common sense exceptions.

I realize that it might not work as well as I hope, or might even make things worse, but the cost seems low enough (compared to the potential benefits, especially if the idea catches on elsewhere) to be worth a try. It would be easy to turn the feature off if it turns out not to help.