For me it's at least 50/50. Maybe not even--the links really are just important as they create discussion on a given topic.
I really, really enjoy the comments on this site.
I really, really enjoy the comments on this site.
Especially because HN shows no summary or anything of the linked article: I'm not going to click on a link if the only information about it that I have is an (often purposefully) abstruse title and a domain name. Once there are a few comments that give me an actual impression of what the article is going to be, then maybe I'll go back and actually read it.