That's not true, and why would you go to the trouble of making a footnote about a six-year-old thread yet skip providing the link? https://news.ycombinator.com/item?id=7566069
grellas' comment has 270+ replies, and HN's software currently paginates threads at 250 comments. That is purely for performance reasons, and I can't wait to be able to turn it off. If you go to the subsequent pages, there are many other top-level comments:
https://news.ycombinator.com/item?id=7566069&p=2
https://news.ycombinator.com/item?id=7566069&p=3
https://news.ycombinator.com/item?id=7566069&p=4
grellas' comment is at the top because the ranking algorithm put it there; many of his comments have gotten upvoted heavily over the years. Moderators didn't do any of that.