That's only true if you choose to introduce a global namespace. There's nothing requiring you to have just a single such catalog of users as long as the canonical reference is the pubkey any more than the contact list on my phone requires you to name people the same on your phone.

(and in fact on reading the protocol specs, they do have a way for relays to publish mappings [1] . EDIT: and that would seem to make it possible for crawlers to crawl relays to assemble non-canonical catalogs fairly easily).

There are downsides to having multiple namespaces, such as e.g. that there's no guarantee that your client will be able to map a given pubkey back to a human-readable name and/or dealing with collisions between mappings from different sources, of course, but this is reasonably well thread ground.

[1] https://github.com/fiatjaf/nostr/blob/master/nips/02.md

Sure, you can have multiple namespaces, and each would have to be censored, but that's about as difficult as playing whack-a-mole with multiple domains pointed at an IP address.

If you can censor the catalogs you can censor the relays. Not least because the protocols allows the relays to serve up catalogs of name to pubkey mappings. Having this lookup functionality makes no difference at all to the ability to censor. If you have an issue with the censorship resistance of this you have an issue with the core concept of this project.

That's fine. But it's entirely independent of whether or not you provide a lookup mechanism for names.

No, you don't. You can have DNS-based aliases to pubkeys, and then people will follow pubkeys and interact with pubkeys, not with the DNS aliases. So if these users are censored later from the DNS then they still keep their identity, their contacts, their followers etc.

That's kind of like saying that people don't interact with domain names, but with IP addresses.

The point of having the mapping of a name to a key is for users to use it in place of the underlying key in their interactions with the system.

The analogy would be valid if IP addresses were permanent and DNS was only consulted once -- and then communication between these two parties was done directly through the IP forever.

Missing the point, which is that the lookup doesn't need to function or be available for anyone but the person composing the message at the time they compose it. It can be entirely private, entirely public, or a mix. What gets transmitted is the pubkey. Optionally the relay can provide a mapping, which may be globally consistent or entirely based in some private mapping.

Users just need a catalog which includes the keys of people they care about. The relays can backfill this information. You have little reason to know mappings for users whose messages you're not seeing, and if the messages are not censored the mappings won't be either.

You could even deterministically map pubkeys to handles with something like bip39. it won't be pretty but it will be unique, human-readable and uncensorable.