Nostr people correctly and truthfully point out that Mastodon being dependent on domain names is unacceptable centralization but seem perfectly content with every zapper being the tenant of the lords ...
Especially with so many Nostr clients (*extremely unwisely*, in my opinion) tying visibility and reach to zaps, it means domain registrars and everyone upstream of them that can apply pressure of control have undue influence upon the social graph of Nostr.