Anonymous Comment Email Verification
Attached is a module that requires anonymous comments to have the supplied email address verified before they enter the normal comment workflow.
The option to verify anonymous commenter emails is enabled per content type.
After verification, if anon users have rights to publish comments without approval, publish the comment. Otherwise, put it into the moderation queue. The commenter is redirected to the node the comment is on.
If verification fails, the visitor is redirected to the site homepage.
If configured, the commenter will be shown a link suggesting they register an account.
I'm planning to create a project for this on drupal.org soon.
Also got 100% approval from coder :D