Are "Blogger" blogs DoFollow in the comments section? Or are they a complete waste of time when trying to build backlinks to boost pagerank
There are certainly better ways to build backlinks or "boost pagerank" I would say, yes, its a waste of time. Try adding your links to directory, guest-blogging or link baiting
AFAIK, it's a dofollow if your leave a link on your comment but the link from the commenter name is nofollow.
What do you mean if your comment is "proven"? As in its approved by the moderator who manages the blog?
Only dofollow blog can give you back link. Instead search for dofollow blog on the search engine. Proven comment above means you should put up only useful comment. The blog owner often have to moderate your comment before acceptance.
We never check for the page rank for the inner pages so if we only comment on dofollow blogs but also have the pagerank to that specific post, then it can be a backlink which counts worth but the fact is, it's pretty hard to search for such pages.