People with less karma need to avoid downvotes and flags because it affects how they can use the site - it affects the rate limiting they get.
(And because they don't know that they can email dang if they think they've been unfairly flagged.)
I'm pretty sure that's not it at all[1]. I can see (and personally do these days) avoid[2] certain types of conversations because of all the down votes. It has nothing to do with not sincerely holding the belief, and it has everything to do with not wanting to expend the energy on comments that aren't actually going to be seen[3]. As you know, as a comment is down voted it turn grayer and grayer. Plus, if you're not as articulate as you wish you were, you are just going to feel frustrated that you couldn't get your point across.
This board, for most, takes up free time, and people tend to want to enjoy their free time.
1) in fact, that statement does rankle the feathers a bit - I've heard a variation that was meant to silence people
2) not very successfully at times
"Hellbanning" is a form of banning where the site takes steps to avoid tipping you off that you've been banned. It's ostensibly a defense against spammers and trolls, who will create new accounts after being banned.
For the past couple years, bans on HN are announced publicly. They're not automatic; the moderators do it directly. It's not based on your karma.
For the most part. We don't do so for spammers or (sometimes) serial trolls.
Top-level comments that are literally seconds old are typically posted about 2/3 down the page. None of my votes appear to actually count. It's been this way for several months.
I'm used to it, but it's still very annoying and I wish HN would actually acknowledge they do this.
If you have a belief that can't survive HN downvotes, to the point where you'll hide it simply to avoid those votes, you should consider how sincerely you hold those beliefs.