Although Keychat uses NIP-17, it already suffers from compatibility issues with other clients that use the same NIP due to the signal protocol. Synchronization is a major advantage for increasing the adoption of Nostr messengers; furthermore, the NIP-17E approach is much better than the current one, and i believe the same effort was made to replace the NIP-4 should be done. Cody is still developing the NIP-17E, i believe you two could help each other, you're my two favorite Nostr clients.