A curious thing by default blog comments are tagged with 'nofollow'. I understand why this is encouraged by Google as it stops spammers getting free links.
I have been thinking though that as long as comments are relevant and contribute something then why shouldn't I allow comments and their websites to be followed.
After all they are contributing to my site so the least i can do is follow.
So websites posted in comments are followed but they are moderated so no Viagra or sex sites please.