Name

Nickname

The nickname is more like a username. It's bound to the password, and it must be unique.
But it's still server specific because of the self-hosted nature.

Why not gamertag?

Xbox empolyee Eric Neustadter first invented gamertags as an amazing idea to solve usernames being ambigious.
Because in games, you don't really care about the name. If you see two "Jack"s, it's not going to be a problem because you know which one wore what suit or whatever.
Since then companies like Discord have used the idea under the name "discriminators".

In synac, however, we do not (yet) support profile pictures.
This means that seing two "Jack"s is going to be very confusing.
So we solve this by keeping every name unique. Sorry.