In large threads where there are hundreds of comments, I find myself frustrated at times with the way comments are displayed.
1. They don't seem to display in order so new comments coming in can appear anywhere making me have to scroll through all the comments again just to find the new ones (even with browser plug-ins that highlight new comments).
2. There is no way to just view top level comments (yes, I have a browser plugin that allows me to collapse comments, which I think HN should do on its own, but I'd have to manually collapse each one just to read the top comments). Ideally I'd like a fast way to view all top level comments by default
Some threads where this immediately becomes applicable are threads like "Who's Hiring" and "Idea Sunday", etc... I'm sure there have been other popular threads where comments just grow out of control and I wish there was a better way to manage this.
Collapsing comments is something we'll definitely be implementing. Collapsing all comments does sound useful.
The problem of finding new comments on popular threads is tricky. I'll probably always lean towards the most minimal change possible for a community as active as HN.
A light way to do it would be to have some visual indicator that makes new comments easier to find. Another way to do it would be to have a separate view for each thread that's like /newcomments (an RSS feed wouldn't hurt either) I may play with providing sort options that does this dynamically with JS.