Google has updated its position on blog commenting in this post on their official webmaster blog:
Hard Facts About Comment Spam
What is clear from the post, crystal clear, is that Google is out to spot and “at best” ignore your efforts:
“Google has an understanding of the link graph of the web, and has algorithmic ways of [...]

Google’s new Caffeine technology is close to being released, and the impact will be felt in your website’s page rankings. If you haven’t already done so, now’s the time to do some research to get a sense for how these changes to Google’s engine might affect you and your business.