Too often, comments seem OK and I approve them, only to receive a failure notice from the respective mail server saying the commenter's address was not valid.
I doubt there's anybody in the known universe who would approve a comment after learning that the commenter has been dishonest. Therefore, I suggest implementing an email address validation mechanism before the comment even goes to moderation.
This could be done in 3 ways:
- Interrogating the mail server interactively and giving the commenter a chance to correct, in case it was an honest mistake
- Interrogating the mail server after saving the post as "hidden" or some other temporary status and setting its status to "pending" or "deleted" based on the result
- Sending a confirmation link to the commenter, saving the commend as "hidden" and setting it to "pending" only after the confirmation link is activated
Of course, once an email has been confirmed, it should be saved and never validated again.
I have thought of accepting comments only from logged in users, but it can be intimidating for some people (it implies being put on a list and getting spam) and is therefore not suitable as a validation solution.
Actually, now that I think about it, I've had failure notices from user registrations, which means that option 1 above could be used also to verify user registrations instead of the confirmation link.