How blog commenting help to improve search engine ranking. most of the blog provide the no fallow link in comment.
Well by comenting and obtaining link from related/niche bklogs you get related backlinks .... that help rankings But theres nothing magical in blog commenting ...
Actually it depends on two things as nature of the blog and nature of the back link. If blog is having high PR and the links are dofollow in nature, obviously, it is going to add positive value towards ranking.
I don't like this method but then again it does bring in backlinks. Make sure to find dofollow blogs to comment on, this will build your backlinks and bring you up in serps.
Blog commenting helps in forming meaningful relationships with fellow bloggers and marketers as well as your associates or colleagues in your industry. Through this, you will not only be able to gain backlinks and site visitors, but also great sources of help and other information that may aid you in making your business succeed further.
If the blogs are having do follow attribute then that will improve the rankings otherwise..it wont help.
If you post comment on do-follow blog with relevant them base topic then it will give you back link and your keywords popularity of you know how to use your keywords in comment