There are no safe haven registrar that are immune from harassment against lawful contents. There's no guarantee that you can port-out domains against registrar's will, even if it's technically your property.
The whole "we can just use DNS names as ID and it'll be unbannable" idea is just relying on the fact that domain names aren't normally used as social media IDs and that more neutrality is expected from registrars, and neither of these presumptions are guaranteed.
Once enough users start using domain names and gets >100k daily likes with anime illustrations, same people as who were problems ARE going to get mad and set up their systems to just hammer Namecheap, GoDaddy, Gandi, Porkbun, until their support gives in just like it always happened. If they didn't, they inject faults in credit card payments, make their authoritative servers unresolvable in UK, Apple devices, on 1.1.1.1 and 8.8.8.8, so on and forth, until they do.
What are you optimizing for and what's your threat model? Personally I'm optimizing for UX and data ownership. One reason centralized services are bad is they tend to turn into monopolies. Once there's no competition there's no incentive for UX to be good. More ads, less useful features, more useless features, etc.
Using a decentralized protocol and providing custom domains is sufficient for me.
If you're optimizing for censorship resistance and your threat model is that registrars want to take you down because there are enough people mad about what you're posting, you're going to have to make UX tradeoffs that most people don't and shouldn't need to.
> If they ban you then you take everything, including your profile domain, ...
This reads like censorship resistance against moderation/management going insane on its own, to me. And in reality, that rarely happens. It's ongoing on Twitter, kind of, but that's less than once in a decade occurrence, and the crazy element wasn't internal.
What happens more often is some fundamentalist group or something starts harassing companies, often leveraging advertisers, credit card companies, perhaps some backend APIs too, sometimes even foreign laws way outside jurisdictions, to get them swallow their agendas. That leads to bans and insane policies getting introduced.
And, if you look at what happened to Twitter in last few years, I think you can see the latter of above two descriptions is closer to what happened to it; whether it was foreign conspiracy, or purely to that guy's insanity, or politics, it was external force that lead to the situation that necessitated escape. It was sane-ish up to the acquisition.
The whole "we can just use DNS names as ID and it'll be unbannable" idea is just relying on the fact that domain names aren't normally used as social media IDs and that more neutrality is expected from registrars, and neither of these presumptions are guaranteed.
Once enough users start using domain names and gets >100k daily likes with anime illustrations, same people as who were problems ARE going to get mad and set up their systems to just hammer Namecheap, GoDaddy, Gandi, Porkbun, until their support gives in just like it always happened. If they didn't, they inject faults in credit card payments, make their authoritative servers unresolvable in UK, Apple devices, on 1.1.1.1 and 8.8.8.8, so on and forth, until they do.