Almost every day I use HN, I wonder why it hasn't implemented collapse-able comments, comment sorting by rank, and auto-collapsing comments. I understand this

Almost every day I use HN, I wonder why it hasn't implemented collapse-able comments, comment sorting by rank, and auto-collapsing comments. I understand this could introduce agreement bias, but I feel like that's something that could be fixed by tweaking the numbers (i.e. only auto-collapse comments with -20 votes). As it is now, it's easy to game the comments thread by piggybacking off the top comment of a post. This can be abused for trolling or just plain discussion visibility (unfairly, IMO).