In order to post comments you need to register an email address. Doing so will result in a url being sent to the specified email address which when visited will activate that address. Once activated it can be used for posting comments.
The email will not be displayed anywhere and is purely spam prevention mechanism. If something goes wrong and you don't receive the email you'll have to contact me to get it fixed, since allowing more than one email to be sent to a mail address would only add to the overall spam levels.