For me, a friend is a person I can discuss personal topics with.
On HN, the topic is given (the article we comment on), and it is usually not personal. If it happens to be personal, it is most likely not the personal topic I would like to discuss now.
Also, if any of us died today, most likely no one else on HN would ever notice. That too is not exactly what I imagine as "friendship".
Being able to talk to people who are willing to spend time talking back is a basis for friendship, at least in my book.
Friendship doesn’t always have to be so serious.