That's the problem, HackerNews comments aren't supposed to be humorous. They're supposed to be a place of higher discussion. If users/mods/OPs can't be serious, learning and intellectual discussion (the entire point of HackerNews) isn't occurring.
Their use of irony to make their point wasn't at all antithetical to the serious, intellectual discussions you're asking for.
Pedantry, on the other hand, is much more likely to prohibit meaningful discussion.
So are accusations of pedantry when you don't get the humour of a joke ;-)
Your parent was clearly not being serious.
I actually worry a lot about whether or not a comment I make or want to make is "HN enough" or "too much like a reddit comment", what with the emphasis on comments contributing to the conversation. Maybe "a lot" is too strong for what I feel. It feels like a lot for internet comments.
I hope expressing this anxiety somehow contributes. :P
I used to feel that way, then I settled on a simple set of rules. My comment should be serious and make sense to the parent (and if it is I don't really care how on-topic it is, some of the best conversations are tangents), or if it's not that serious, it needs to attempt to be a little insightful (humor is great for bypassing people's preconceptions). If I have something that's neither of those, I'll only submit it if I can contribute something additionally along with it that follows the prior guidelines. Every few days I'll erase the comment I've typed into the box (sometimes multiple paragraphs worth) after reflecting because it's either not relevant enough, too inflammatory, or will likely start a conversation I really don't feel like participating in. Different people have different criteria, but this helps me feel like I'm contributing, which matters to me, since I get so much pleasure out of HN.
I don't know where you got this impression but it's not true