There's nothing preventing you from implementing your own social network with those rules.
Hacker News is a forum for business ideas and web-based technologies after all, built around an angel fund / venture capital slant.
But I'm trying to tell you that you'll end up relying upon user-based moderation for many cases: including simple cases like spam from new users or VPNs. Maybe even IP-based blocking as certain unsavory groups of people tend to cluster around certain IP addresses.
I responded to your statement that 'The _ONLY_ moderating action internet citizens have is moderation [...]'; I'm just pointing out that while that is true for twitter users at present, Twitter could experiment with other approaches if they felt like it. I'm not saying they must or they should, just that nothing prevents them. I responded in handwavey terms because your comment about 'internet citizens' seemed pretty open-ended.
But I'm trying to tell you that you'll end up relying upon user-based moderation for many cases
OK? That's the idea I was exploring. It worked to some extent on NNTP, where people would maintain 'killfiles' and different Usenet groups were more or less protective of their cohesion. I'm not suggesting it as some sort of magic bullet, just saying that centralized moderation is not the only possible approach.
And arguably not, because a huge number of NNTP servers were in fact, moderated. Especially as spam and warez started to appear on servers owned by public institutions (universities and the like), a huge chunk of USENET split into the alt.* unmoderated groups, and the other, centrally moderated groups.
But Twitter doesn't. Hacker News doesn't. Reddit doesn't.
All three of these large Social Media sites require moderators to police the actions of their users. This isn't new or exotic, this is just how the web typically works. Forums, Usenet, Mailing lists, IRC, BBS, its always been like this.
If you want to try to make a new social network with different moderation systems (ex: user-based blocking), feel free to do so. But I've hung out enough on 8-chan to know that you'll have to deal with Swatters and Doxxers almost immediately, who are looking for an unmoderated coordination medium, and they'll take advantage of your features. You'll also have to deal with lesser forms of spam and advertisements: Cryptocoin spam these days, but it used to be Viagra, or Nigerian Prince scams.
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The question isn't "Twitter shouldn't be allowed to moderate its users". The question is if Twitter made the right move here or not.
So now lets actually discuss the crux of the issue: is spreading COVID19 misinformation a big enough reason to warrant a banning? I of course agree with the move. Our hospitals are filling up with the Omicron variant and the vast majority of these patients are not-vaccinated. Twitter leveraging their reputation to say that Marjorie Taylor Green is a net benefit to society.