The more I look into decentralized messaging systems, the more I think user names are a bad idea and trying to implement them is just a waste of time. Nice ones would disappear soon and most people would get a too-long, non-practical one in any case. Opaque IDs and assignable display names are easier and I think more useful.
@caffeine who would assign the display name? Also, https://www.w3.org/TR/did-core/
@jonn
Everybody would assigns a display name to their contacts, exactly as people do with phone numbers (ignoring directories etc)
@jonn
this is understandable for people wanting a well known public profile. But for what I observe on Telegram, some people prefer to have no default display name (in general they choose one-character names like ".").
A nameless identity should be allowed for those who like so. In a design like that, you probably would choose a nickname only when joining public group chats, if ever so.