Naven
Answers
Is it better to sign up with an email address or a username?
An email address for the account, a username for how other people reach you. That way the identifier you hand out is one you can change, and the one that recovers your account stays private.
The two jobs are different and conflating them is what causes trouble. An address used as a public handle gets scraped and spammed; a username used as a recovery credential cannot receive anything.
Platforms that separate them let you give out a handle freely while keeping the address to yourself.
On Naven the address is the login, and a username is the thing you can safely put on a poster.