... but HN has a collapse thread feature?
Yes. Yes. Yes. To the point where I've almost tried to copy some HackerNews source code and complete a POC myself.
Others have commented that this feature already exists. And yes "technically" it may exist, but I'm guessing that you mean "by default". I absolutely agree that I should be able to set collapsible threads as the default.
It never fails on HN, that on some topic, the first/top comment and its replies span the _entire_ page! That's terrible UX! We want to see what other people have to say.
As a user/reader, let me dig into conversations/threads that I find interesting without having to scroll through pages and pages. Who's to say there aren't more interesting discussions buried underneath the top comment thread? Dang always has to post reminders saying to "not forget these pages of comments". If we had a collapsible thread, I believe he wouldn't have to do that as much.
This could be implemented with little-to-no fancy JS/whatever -- so that HackerNews remains as barebones as it is. Even better - if you let users choose whether or not they want the collapsible comments feature by using a setting on the user profile view. Everyone wins :)
There's a collapsed feature.
If you are in a child comment, you can click on next to go to the next comment/discussion
Check out Hacker Brain (link in bio) for pre-collapsed threads.
That's been existing for quite a while now? The "[–]" link at the end of each comment summary line.