Here's a vote for less use of javascript, not more.

I use w3m under emacs, and that does not work with Javascript. So HN would break if it required it. Using a Javascript-aware browser would also expose me to a host of Javascript vulnerabilities.

Anyway, I'd be much more interested in comments and articles getting tags, rather than collapsing comments.

Even better would be ditching primitive web browsers for a return to Usenet, which would allow the use of sophisticated news clients with features like kill files, properly threaded and sorted conversations, advanced filtering, and, yes, collapsible comments.