If you are using the default WordPress registration for users who register via email, users who register in that way will have their email address marked as verified by WP Discourse. Ideally it would be possible to determine which users had registered via social login and which users had registered via standard WordPress registration.
Have you decided on a social login plugin? If so, let me know what it is. If it’s a free plugin I’ll take a look at it and see if I have any ideas for a good way to approach this.