Redmine

When doing an on-the-fly user creation, if Redmine finds that another user already has the email address being retrieved, it allows the user to specify their details (name, email, etc.) to continue. This seems sensible enough for the default behavior of allowing self-registration.

However, in the case where self-registration is disabled, it would be more sensible to have the user request administrative assistance rather than be able to update those details.