I support Hacker News moderating itself however it chooses. However, if we are looking at it as a moderation model for large, open, non-editorial platforms (Youtube, Facebook) -- which I believe should all be covered under public accommodation law -- it clearly fails. And even if when we are looking at ostensibly neutral, publicly-orientated sites like newspaper comment boards, it fails.
Hacker News moderation is not appealable, not auditable, does not have bright line rules, and there are no due process rights. It simply does not respect individual rights.
So while this moderation method succeeds for Hacker News, and perhaps should become the model for small private sites, we should not try to scale it internet-size companies. Platform companies (Google, Facebook, Twitter) and backbone companies (ISPs, Cloudflare!) need a different set of rules geared towards protecting individual rights and freedoms instead of protecting a community.
I'm not sure I'd agree with this. An appeal is as easy as sending them an email. In my experience they're more than willing to hear you out.
We only use shadowbanning when accounts are new and show evidence of spamming or trolling, or unless there's evidence that the user has been serially creating accounts to abuse HN. It's possible we got it wrong in your case, but again, we can't correct mistakes if people won't tell us about them.