I don't really think "scoring" comments at all makes sense. I'd much rather systems like reddit do away with downvotes and point displays entirely, and only allow you to express your desire for something to be seen by 'upvoting'. That would influence it's sorting order, but nothing else. Users no longer get the dopamine drain of seeing "-15 points" on their post, and you stop seeing people edit things with "really? downvotes?". If someone disagrees so much that they need to express it, they should reply directly to the post.

HN as it appears to regular users is pretty close to my ideal system, except that it greys out heavily downvoted posts and you can see the number of points you have personally.