Hacker News Enhancement Suite [1] is pretty great with collapsible comments, even shows you new comment count after you revisit home page. Styling may be a personal taste thing though.

[1] https://chrome.google.com/webstore/detail/hacker-news-enhanc...

Not only does it show new comment count, it highlights the unread comments in the thread itself.

I've become so reliant on HNES that I avoid accessing hacker news on other devices (and when I have to, I use hn.premii.com).

https://addons.mozilla.org/en-US/firefox/addon/hn-utility-su... does the trick if you are on Firefox.

Chrome extension to collapse HN threads: https://chrome.google.com/webstore/detail/hacker-news-collap...

I didn't read this thread all day for that reason. Now I'm at home with my tablet and can swipe to collapse that giant swath of gibber-jabber.