Don't use blog comments for SEO, you will only gonna hurt yourself. Of course, if you have 1% of your links coming from blog comments, it may actually help you in your link diversity profile or if you are building a churn and burn project, they may be handy, but if you want sustainable results - don't use them. There are also huge headaches because of the negative SEO attacks, as you see the stupid G can't distinguish if a guy build these comments on his site himself or if someone else hired a Fivver guy for $4 with Scrapebox in his hands. I hope that Google will start one day to ignore these links instead of punishing webmasters if someone use them for negative SEO. We are 2014 and soon it will be 2015. We should always be up-to-date, unfortunately too many people are stuck in time. "Survival of the fittest" - things are always changing and we should always change too, if we stop - we are dead.