Not controversial. Just not aligned with the owners of HN.
The comments you upvote/downvote are used to calculate your "opinion similarity" to the owners. Then your upvote/downvotes are modulated by that similarity. It's a way of using other humans to amplify the opinions of the owners -- they don't have time to read all the comments, so instead they filter out those who think the same way they do and let them do it.
I've contacted HN before and they've told me they auto-downvote certain kinds of content. It's not a stretch to assume their views are influencing that criteria.
Oh yeah, I think I remember reading they demote submissions that they think will cause low quality discussions. I don't think that's related to downvoting or your karma.
The comments you upvote/downvote are used to calculate your "opinion similarity" to the owners. Then your upvote/downvotes are modulated by that similarity. It's a way of using other humans to amplify the opinions of the owners -- they don't have time to read all the comments, so instead they filter out those who think the same way they do and let them do it.