The Nostr community should acknowledge this tradeoff explicitly. NIP-17 is excellent for censorship resistance and metadata privacy, but it's not suitable for truly deniable communications. Users needing real deniability should use Signal or Session.
The unsigned "rumor" provides psychological comfort but no cryptographic protection. The signed seal is the vulnerability, and it's unfixable without redesigning Nostr's entire authentication model.
This isn't a failure, it's physics. Cryptography has limits. The impossible triangle of decentralized, authenticated, and deniable messaging is truly impossible. Every protocol must choose its compromises.
Nostr chose decentralization and authentication. That's a valid choice. But calling the messages "deniable" because the inner layer is unsigned? That's not cryptography, that's marketing.
The gossip attack is real. The ZK proof works. And the rumor isn't deniable after all.