Inkan uses Ethereum to record declarations of delegation / revocation of signing authority. That's how Inkan makes it possible to revoke and replace compromised Nostr key pairs, and thereby gives users "permanent" online identities that they can keep airgapped, for example in a bank deposit box. I think that's precisely the type of use contemplated by this article. But "public bulletin board" may not the best term for it. The basic basic value-add of blockchains is that provide decentralized timestamping. A better term would be "public timestamping service."