Can I remove/bypass the requirement to have unique email addresses?

I have no idea why but my backup plugin dropped most of my wp_users table from my database. Fine, I thought, I'd re-add my 1400 missing users with Batch Create.

The problem is that Batch Create has spotted that the email addresses of all the missing users are still in the database, principally in wp_registration_log.

Can I safely comment out the bit where Batch Create checks this, seeing as I know every user will just be restored to where they were before? I know I won't end up with multiple accounts sharing an email, I just need to re-associate them all with row in wp_users and give them privileges on the right sites.

(My hosting company's backup of my DB failed apparently .....! Nightmare.)

Failing this - if there are any MySQL boffins here - can I drop in the wp_users from an older backup of the database (the users haven't changed) or would this be suicidal?