But how do you enforce that? Bitcoin doesn't recognize names natively. If I write a transaction that says "the name ursuscamp belongs to me, here's my pub key", what will stop you from also writing a transaction later that says "the name ursuscamp later belongs to me, here's my pubkey"?

The only answer I can think of is soft consensus, like first come first serve. Unless you can come up with some scheme that gets Bitcoin to treat names as native assets, such that if you attempt to publish a second transaction also claiming a name, nodes will reject that transaction as invalid.

We might just be talking about the same thing, since you're referring to inscriptions, which are themselves really just a social convention.