Is there some benefit to making users scroll through every single comment? Reddit has this feature by default. I use a GreaseMonkey script that adds the functionality to HN, and when I browse from another device, I'm reminded how tedious it is to scroll through a long comment thread just to get to the next root comment.
And the fact that leaving a comment takes you back to the top of the thread... I love HN for its content, but it's certainly not a marvel of usability. The expired link issue is ridiculous.
http://userscripts.org/scripts/show/110317