Ironically this post is doing wonders for its page rank, as people are linking to it in the comments
Now that we have better ML, maybe we could take "link sentiment" into account too.
rel=nofollow is used to signal that links should not be used by search crawlers for authority calculations on most sites with user-submitted content, including Hacker News.
You basically have to use nofollow for comments otherwise your site becomes a big target for SEO link spam.
I wonder if we ought to be flagging it then? There's already so much uninteresting AI slop observations.
(By coincidence, see also https://news.ycombinator.com/item?id=47641829)