The thing I like most about (commenting on) HN is that it's incredibly easy to predict if a comment will get karma or not. HN is slow enough and the comment listing algorithm works in such a way that if you post during the first half of a submissions life your comment is guaranteed exposure and if the comment has value it'll float to the top.
I don't think I've ever posted a comment and felt that the score (or attention) didn't fairly reflect the value of the comment[1]. Something about the uniformity is very reassuring, unlike reddit where you need to either be in the first 5% of comments or provide something seriously exceptional that appeals to every reader to even have a chance of being listed near the top of a submission.
From my experience the "best" scoring comments are easy to pinpoint why they've scored well and if someone was so inclined they could very easily spend their day "farming" karma here, but if someone were to do so they'd be benefiting the site because the only real way to obtain karma here is to provide value. Even if that value is trivial (like mentioning a relevant article, or giving a brief anecdote that validates a point) it's still value.
[1] Sometimes controversial topics result in "unfair" scores, but they're also very easy to expect before hand and generally if you post something controversial you'll get good enough discussion from other users that it's never a question of "I wish I knew why people gave me that score!" which is the most frustrating thing.
Most of the time this is true, but I've certainly had comments like this one[1] where I thought maybe deserved some upvotes, but an order of magnitude more than what I would consider other good comments. And sometimes I post what I think is a wonderfully insightful post about how simplified memory access methods are the most important part of RISC nowadays and nobody upvotes it.
It's easy to mistakenly believe HN is meritocratic if you have enough HN celebrity for people to seek your comments out. My comments with the least thought behind them get the most upvotes. Those with the most thought pass by unseen.
It's a powerful disincentive for putting much thought into comments.
It is not only the algorithm which works so. Our brains also in a similar fashion; we first try to find out whether someone else's comment resonates with our impressions or fragments of what remains in our minds after reading the story.
So I upvoted you because you wrote first. You have to first mover's advantage. And I believe it is fair.
The first mover advantage goes beyond increased exposure. It means that one has maximumized their ability to shape the direction of the conversation in alignment with their thoughts. Because early comments are more likely to draw responses, the top poster in a thread has the most opportunity to clarify and extend their thoughts in follow-up responses.
Follow-up responses will tend to be received in the same vein as the initial post, and if the initial post gained traction the one's follow-up is likely to garner upvotes as well.
I tend to up-vote a good deal of comments, but -- like you -- I do it more the first time I read a post's comments. So, any comments written before I read it are more likely to get upvotes than any that are written later and which I see on later visits. (This is compounded by the fact that I'm trying to cut down my lurking on HN, since it's so easy to keep reading all the good stuff that other people write.)
I don't think I've ever posted a comment and felt that the score (or attention) didn't fairly reflect the value of the comment[1]. Something about the uniformity is very reassuring, unlike reddit where you need to either be in the first 5% of comments or provide something seriously exceptional that appeals to every reader to even have a chance of being listed near the top of a submission.
From my experience the "best" scoring comments are easy to pinpoint why they've scored well and if someone was so inclined they could very easily spend their day "farming" karma here, but if someone were to do so they'd be benefiting the site because the only real way to obtain karma here is to provide value. Even if that value is trivial (like mentioning a relevant article, or giving a brief anecdote that validates a point) it's still value.
[1] Sometimes controversial topics result in "unfair" scores, but they're also very easy to expect before hand and generally if you post something controversial you'll get good enough discussion from other users that it's never a question of "I wish I knew why people gave me that score!" which is the most frustrating thing.