[birracerveza]

I agree on all points, except the last one.

If you can downvote, your comment WILL be downvoted based on ideology. No exception. HN is much, much less guilty of this compared to other sides (especially Reddit), but that doesn't mean it doesn't happen. If it can happen, then it eventually will, and considering a single downvote buries the comment this a big problem. The real issue resides in using upvotes/downvotes to sort content to give "good" answers more visibility, so unless you only have text at your disposal to express your agreement/disagreement you're ALWAYS bound to have a biased echo chamber.

[caslon]

A single downvote doesn't bury the comment. Multiple downvotes, however, do. A single downvote isn't even guaranteed to change a comment's placement.