NoFollow Links on Blog Comments Will NOT Hurt Rankings
It's not easy building links, but SEO's should know that shortcuts are rarely (if ever) the answer.
Blog comments, which can be useful when used strategically and more importantly thoughtfully (contributing to the conversation) can definitely contribute to a natural, meaningful link profile for a digital presence, but it's easy to go overboard sometimes.
Google's Matt Cutts has posted a new video (shown below) answering a question about whether nofollow links on blogs can damage a website (we can assume that website’s ranking). Cutts indicated that too many nofollow links do not typically hurt a site but a manual spam action might be taken if there is enough comment activity that is or can be deemed deceptive or manipulative.