If you know it's real name, you should not write it anywhere, even encrypted or whatever because clients can get access to unencrypted data when you use them. It's up to you not to doxx your friend, just like you wouldn't reply to a kind 1 post of is with "hi bob!". My point was, anyone with access to sensitive information should not put it online on a social protocol, or at the very least, not on a public list like you said. This doesn't mean petnames shouldn't be used on public lists. Also you could just make a up a petname that you can recognize without explicitly doxxing him.