From what I can tell... Whenever an email has been entered in the registration box and inserted into user_signup_email_verification table, trying to re-enter that email before clicking the registration link fails to resend or give any meaningful notice. A bullet point appears below the input box (as if to give a failure message) but there is no message. Email doesn't necessarily have to be sent for this to occur.
If a user does click the email link and register, the module handles it correctly and notifies them that the user already exists.
From what I can tell... Whenever an email has been entered in the registration box and inserted into user_signup_email_verification table, trying to re-enter that email before clicking the registration link fails to resend or give any meaningful notice. A bullet point appears below the input box (as if to give a failure message) but there is no message. Email doesn't necessarily have to be sent for this to occur.
If a user does click the email link and register, the module handles it correctly and notifies them that the user already exists.