If we find a high PR do follow blog page (not blog/site) then we make a comment in it, the backlink is through our name. Is this an effective way? Google will surely able to discern which one is a genuine link and which one is just a blog comment
Sure the comment will add some value. But the point is where your comment is. Be sure that the blog post page has a high PR and not the blog!
"Be sure that the blog post page has a high PR and not the blog!" Well, the page may have <1 pagerank, but still can be useful
If do follow tags are present, then there are a couple benefits. - Counted as backlinks - You can have the keyword used instead of your name, to target your site for a particular keyword although it looks odd. Btw my blog too has a do follow
There are rumors going around that spam commenting works again and people go around with scripts dropping thousands of links "pray and spray" style.
commenting on blogs leaving your website is very effective. i gained about 100 backlinks from commenting on blogs for free for people, it makes both of us happy.