Let's take a look at the login model for multiple sites. 1 site or more, with account or not.
Let me explain this table.
- A: Unknown user arrives at a SE-site.
- B: Registered user has an account at a SE-site.
- C: Registered user arrives at another SE-site.
- D: Registered user has an account at another SE-site.
The natural order to transverse through this is from A to D (z-order).
- User role A is an Unknown user (either new or logged out).
- User role B is a logged in user.
- User role C does not exist in SE (visitor role).
- User role D is a logged in user.
Let's look at the actions that any role can take.
The user B can go to D with the Global Network Auto-Login feature.
The visitor role does not exist. On SE any user that visits a site where he/she does not have an account, (s)he'll be treated as an unknown user (role A).
I propose the C role (visitor) should be created. Any B role (known) user that visits another site is known to the system, but has no badges nor points at the other site. A 'create account' link is presented, so the user can become a D role user with one click. Otherwise, the visitor behaves like an A role user (unknown).
Note that I haven't mentioned the auto-create account feature. That is because I am against it, just like anybody else.