I pretty much loathe all automatic comment moderation and sites which push for registration in order to comment. A quiz is easier to read, could actually be something related to your niche/ site and no one has to give away their privacy/ set up an account.
I wish this quiz option extended to user login and registrations on WordPress. I was using a mailing list which worked with the users registering on my site. This was a huge aggravation because I could not pick out the 1% of legitimate registrations versus bots and idiots who wanted to leave spam.
Also wish this was a feature in the megashark aka Jetpack. It would likely get better developed, or at least get more attention there.