The thread is https://news.ycombinator.com/item?id=22865357, which is the page you've been posting to. It's now listed on the front page of the forum, https://news.ycombinator.com/, which is a list of the stories people have upvoted today.

You're not the only person who misses the old newsgroups! The format that Hacker News uses is one that became sort of standard on the web in the early 2000s. It works differently than usenet did, but you get threaded comments in the sense that replies are nested under the posts they're replying to.