Hey! They actually replied to the last email!

From: support@register.com
To: paul@roub.net
Re: SafeRenew billing failure

We would like to apologize the inconvenience caused to you
due to the SafeRenewal(TM)Service. 

We understand that you domain name has been successfully 
transferred from Register.com and the current registrar of
your domain name is R91-LROR.

We have successfully deactivated the domain name from our
databases and henceforth we assure you that you will not
be receiving any emails regarding this domain name from 
our behalf.

So good, eventually, for them. Of course, the emails weren’t my real concern – more that, had they had updated credit card information from me, I’d now be attempting to get some unwarranted charges reversed.

Take what you can get. At least they’re not domain-squatting weasels