Given that the content quality here is high, chasing karma could be a good thing, if it encourages additional high-quality, thought-provoking discussion. People should be rewarded for sharing content like that.
As a corollary to my point, we'd also like thought-provoking material rather than pure provocateurs. But I'd take an intelligent provocateur over a philosophically/historically uninformed HN comment any day of the week.
As this brief discussion of the HN metagame shows, anything that gets a number stuck next to it will attract people to optimizing it like flies to a manure pile...
Mostly I upvote if the user posted interesting/useful information.
Sometimes I upvote things I disagree with if I think it promotes a good discussion.
This also seems like one of those things where Goodhart's law may apply.