I don't think the moderation team sought out to create a monoculture- is that what you are suggesting? Downvotes and upvotes for comments for many people are viewed as ways to reward/punish well-constructed/poorly constructed argumentation. I'm sure originally it was a way to conceive of a popularity rating for an article/post. Something with tons of upvotes is popular.

I think I'm offering this as an alternative to the theory that a monoculture was intentionally created, which is one which the mod team disclaims as I understand it. But if every individual moderation decision is made on the basis of "disagreeing with the 'accepted' answer is trolling" or something like that, and the HN community is [self-]selected on that basis, then I think that's an equally good or better explanation for what I actually observe in comment sections.

There's something to be said that the monoculture path or end result - if that's what we think is the trend - is more a function more broadly of either technology or some cultural norm. Because it's so incredibly widespread outside of HN, the comment voting behavior here seems to me more like a symptom of a broader problem than a design artifact.