I have implemented your plugin in one heavily commented blog. And your plugin works quite well
However, I have a few suggestions:
Settings in use: Splash screen & moderate even after email verified
1. regarding verification link, on first click, it works fine
but on second click, it shows message "address could not be verified".
2. When an email address has already been verified previously, then the comment should automatically show that email address verified - instead of sending the verification email again.
Another variation that can be done is that if an email has been verified within certain period - say previous 6 months (best if user configurable) - then the comment status should automatically show as email verified.
3.Perhaps there should be a page listing all verified emails.
I'm using your plugin at: http://indiapoint.net/ca/