For those of you who are subscribed to the GitHub notification email messages, I certainly feel bad about all the spam that you're receiving. Unfortunately, it's not something that GitHub gives repository owners the power to control; it's been reported to the GitHub administrators who will eventually block the user universally.
As a reminder, you're able to block that user from sending notifications to you personally; go to one of the comments and click his username to go to the accounts page. Kind of in the upper right region, there's a small dropbox which has options to both block the user and report them to GitHub (which you may wish to do).