If you're really interested in valid SEO, please do not
run around dropping links in blog comments. Real SEO has nothing to do with crapping up folks' comment streams with bogus links.
Consider: legitimate bloggers will recognize you as the spammer you are and never allow your comments to see the light of day. So posting a bogus comment to a high-quality blog in the hopes of gaining a link is simply a waste of your (and the blogger's) time.
If you find a blog that does let those kinds of crap comments through, though, it's not much better use of your time. Those blogs that do allow link drops probably don't have any "link juice" to pass along, as they most likely been flagged by Google due to the high quantity of spam they contain (mostly from clueless so-called "SEOs" spamming their comment streams with irrelevant comments and links).
Please do not be dumb enough to think you can fool bloggers with lame posts such as "I really like this blog. You have such insightful thoughts. I wish you would post more articles like this." I see plenty of these on my own blogs every day, and I mark every one of them as spam. Because that's what they are.
If you're posting in blog comment streams to try to get links, if you think blog comment spam has anything to do with SEO, you're doing both SEO and blog commenting wrong.