On: Don’t record your social life on an append-only so...

[jfax]

>Your identity isn’t a username and doesn’t depend on a domain name or service provide

Like a tripcode?

>Instead, your username is a meaningless cryptographic hash that consists of random-looking numbers and letters.

Ah

[grey_earthling → jfax]

In SSB it's a public key. Most users announce their own display names (which needn't be unique) and some clients let you set a pet name for other users (like a phone's contacts list).