I have two Stack Exchange OpenIDs (different emails). Both are logins for my Stack Exchange accounts. I do the following:
- Remove one of the logins.
- Log out
- Log in to Stack Overflow with the removed login.
- I get the create account page (as expected).
- After confirming the new account, I'm logged in to my old account
- Both logins are listed again under "My Logins"
So it is impossible to remove a login.
When replacing step 3. with "login to StackExchange.com with the removed login" I get the "Oops! Something Bad Happened!" site. Afterwards the same behavior.