I turned off comments for most of my blogs because 99% of the comments were spam. I got hit so hard by the Chinese comment spammers that it overwhelmed Akismet and shut it down.
I don't think a comment does any good for driving real traffic unless the focus of the blog page is directly related to your site. If it is not, then any traffic is non-targeted and is probably useless.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin