Because you can't downvote an HN post, and shouldn't downvote when you disagree, so people end up upvoting contrary opinions they agree with. The sequence is us

Because you can't downvote an HN post, and shouldn't downvote when you disagree, so people end up upvoting contrary opinions they agree with. The sequence is usually [Post with a position A] -> top comment (disagrees with position A) -> top child comment (disagrees with top comment, usually focusing a single, least-significant point raised by top comment)