No, it's selective evolution towards comment that appease the majority of the commenters, which is different. It's how you end up with reddit-like echo chambers.
A) that’s within the realm of what I wrote, so it doesn’t inherently disagree
B) that also happens, there are also insightful things people hadnt previously thought of that people just like
C) as others wrote, only a subset of users can really affect consensus. So its more of a representative democracy, active users that have accumulated alot of karma are the ones that have to simply be unoffended. But others can flag and effectively censor anyway.
The majority of Hacker News users can't downvote, and because of that, you're almost certain to get more upvotes than downvotes, unless your comment has few redeeming qualities.
The majority of Hacker News also doesn't really upvote much. Your typical front page post has under a thousand votes, and posts are the easiest things to upvote. Comments rarely get over a hundred, and almost never get over three hundred.
A single vote can change the outcome of a thread. A reply, even a vicious one, can increase your chances of getting votes; there's a phenomenon in which people will upvote comments they dislike and or disagree with in order to have their response be higher up.
This does mean that HN punishes certain styles of particularly offensive or non-contributing comments, but most won't be punished at all. It's, like vmception pointed out, a system that encourages comments that do "well enough." Because there's no punishment in making a mediocre comment, there's always reason to post. Even people saying absolutely rancid things ideologically aren't likely to get downvoted unless they frame their comment wrong.
HN is about style more than it is substance; it's not an echo chamber, because it doesn't select on ideology. It selects on how pretty your words are.
It very much is, to the point that this place is derisively called "the orange website" by those who can see it for that. You might agree with the precepts so it doesn't seem that way to you, but the sooner you can recognize them, the better off you'll be.
I derogatorily call this website "the orange website." That doesn't make it an echo chamber. For as many awful opinions on political topics or type systems there are on this site, there are people who object to them and comment that they do. Hacker News has a tendency to let people say offensive things; this doesn't make it an echo chamber. It doesn't make it good (about 1/5 of the threads are good), but it doesn't make it an echo chamber. Even things that should be pretty much just echoes, like threads about people who killed themselves, often aren't. Because even when someone has killed themselves on this website, people will always come out of the woodwork to say that it was their fault, in contrast to popular opinion. It's not an echo chamber, it's an amplifier.
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.
B) that also happens, there are also insightful things people hadnt previously thought of that people just like
C) as others wrote, only a subset of users can really affect consensus. So its more of a representative democracy, active users that have accumulated alot of karma are the ones that have to simply be unoffended. But others can flag and effectively censor anyway.