I'd probably just abolish downvoting entirely: rely entirely on upvoting. There's already a bias towards upvoting in the system due to the min cap but not the max cap.
You make it sound like voting-as-disagreement is rare but in my experience it's by far the most common way downvotes are used. I have showdead switched on and I keep toying with the idea of finding an extension to un-grey comments, because over and over I find comments in grey that are well written, erudite and merely express an opinion that goes against the current startup-culture HN zeitgeist. They aren't actually bad comments though.
So why not just let good comments rise to the top.
Perhaps you are right. I have experienced downvotes primarily in semi politicized discussions like automation, economics blockchain, diversity discussions. Most technical posts seems fairly balanced.
Perhaps yeah abolish downvote and only have flag for admins and people with high karma is a good idea.
That seems like a decent idea but a bit tedious for the voter. I also like the Stack Overflow model where each downvote costs 1 of your own karma points.
If I was allowed to make one change on HN it would be that a downvote had to be accompanied by a comment as to why the downvote happens.