I have written comments on articles that were posted before. In many cases the discussions and participants are quite different. And they complement the comments of the original post.
HN completely random, yes there are patterns, but if you looked at 1000 articles that have been posted 5 or more times on HN you would see it’s completely random to if a topic get attention or not. Same with an emerging new story, multiple users will post it and frequently only after it’s posted a few times over hours or days does it get traction; and even then, there’s obviously a lot of posts that never get attention, but do elsewhere, but were within the scope of what’s on topic on HN.