If you could actually do anything to help this user, you would do so(would of done long before now) and be confident about it. There is no try. You do or you do not. As it's just one field in a database, it shouldn't take too long.
But back to the actual point behind involving myself in this affair, as you are aware - and for some reason intentionally choosing to avoid confirming - this forum was generated in order to pull Asgardian affairs from retardations such as facebook, minimally for the privacy concerns such service warrent.
So, with that in mind, why are you attempting to encourage this user to give FB a copy of the email address they will be using for Asgardia services as well as the other conversational details that will transpire, including all the applicable security questions you should responsibly be asking?
This is not the only chat method available at all, and it's possibly one of the least intelligent to attempt to utilise. It might be the only one you know how to use, but there's plenty of secure methods that could be employed. It wouldn't even take 30mins to embed one into this service.
If you'd truely want your account gone, Chris, I'd suggest an email to: citizens@asgardia.space or to open a thread in the feedback section specifically requsting account removal in both the topic and body in order to confirm you'd want the account gone. Again, nuking the account simply to change the email isn't clever.