is there any way to allow duplicate user names and email addresses for whole system but unique for a domain ? Or maybe better way is to allow duplicate user name but unique email address. This could be portable across blogs.
I thinks there should be 3 or 4 parameters for registering/login
- email address
- domain (only in Multi site mode, check with DB table wp_usermeta/wp_blogs)
Domain may be visible (for common login system in enterprise network) or invisible (transfer from URL as domain url)
Have blogs Site1 and Site2. This sites are different, no common user.
Create an author account with login "john.doe" and email "firstname.lastname@example.org" for Site1.
In the Site2 is author with name John Doe. But it isn't same person, only have same name. When i want to register user login "john.doe" but with email "email@example.com" i get an error for duplicating user name.
I think this is a remnant of earlier versions of WordPress. By version 3, this should not appear.
Or have Example 2:
Have 2 sites, Site1 and Site2. Again different sites. Both sites offer subscribing newsletter. So, i want to register on Site1 with name "john.doe" and email "firstname.lastname@example.org". And now, i want to get newsetter from Site2. Want to register with same user name and email and oops, get an error user name or email existed. How can exists when i'm not registering before ?