Some techniques for blog commenting, in case you need. www.cosmocentral.com/post/2007/12/Marketing-by-Blog-Commenting.aspx
To add: don't forget that most wordpress blog comments left have no-follow tags that are not as useful for backlinks if that's your main goal of blog commenting.
Blog commenting no good for rank anymore as you said. But it could be used for traffic nicely, if used right.
Of course, if the site's link is relevant to the blog and the comment is insightful it could drive traffic to one's blog
Most blogs now have the "nofollow" tag attached to links in blog comments. And Google does not pass any PR to a link with the nofollow tag. You can get a little traffic by commenting. Also, if your comments are helpful or memorable you build your reputation over time which leads to more traffic as well.
I will add another point. Not all search engines care about the NOFOLLOW tag. Many of the search engines will take it as a backlink counted for ranking. But Google doesn't as explained above.
Check out the site www.DoFollo.com It's a google powered search engine that only returns blogs WITHOUT nofollow. No, this isn't spam, IF you have something good to say. If not, then yeah it would be spam.
Commenting is not spam at all. It allows you participate in other blogs, let your name known to others.
You can view the source code to find out that. Right click on somewhere on the page. Click on "View Source". That will show code on another page. Find link <a> tag there. Nofollow tag generally looks like this: <a href="http://www.cosmocentral.com" rel="NOFOLLOW">CosmoCentral</a>
I just wrote this a little while back it's some great reading have a look and post a comment, http://forums.digitalpoint.com/showthread.php?t=588569 THIS IS MY 1000 POST