What I really would like to have would be to collapse comment threads via a column that runs the length of the comment thread and is indented like its respective comment.
This way I don't have to scroll to find the comment to collapse its thread, and clicking the column is easier.
This is used in some subreddits in the old Reddit style, e.g. /r/de as can be seen here: https://old.reddit.com/r/de/comments/rcc9us/experten_finden_...
The Refined Hacker News extension for Chrome has a “collapse root” button on each comment that I think does what you want.
+1 for the extension. Been using it since forever on Firefox and Brave.