No. It will be a new certificate and he’ll need to ask his contacts to update the certificate they have for him.
No, Comodo never sees the private key for the certificate so the user can’t have the same certificate back. It is the responsibility of the user/corporation to back up the user’s certificate with its private key.
I have had a similar problem; I had my office computer formatted and reinstalled with Windows 8. I forgot to take a backup of the free email certificate and I dont remember registering a code to revoke the certificate.
Now I want to setup a new certificate for my office email address, but it says a certificate has already been issued for this address.