Bug: Multiple users cannot have same email address

When I upgraded to 2.8.2, the ability to register multiple users with the same email address disappeared. This is seriously annoying, since now I have to make up fake email addresses for some accounts.

I can sort of see how it might be beneficial not to allow users to register themselves with the same email address, but I don’t see why admins should be unable to do so. Could you please, please, please bring back that very useful feature?