I think it would be a good interface feature to have them show the first few and last few characters in the npub. Discord has numbers for users as well, that's a combination system. It's easy to see how there can be easy scope for bots now and spam and scam... Yes, keet.io lets you define one with the identity you exchange with others to structure the chat log. It doesn't expose you to the key at all though, which annoys me.