you can get back links by commenting a blog, but if you comment a blog just make sure that it is full of sense and interesting. smart comment will make you and your site popular. more popular you are a better and more backlinks you'll gonna have.
Blog commenting is useful to create a good quality of backlink. These backlink increases the website visitor. If you do your blog commenting into referral or niches website then you could get more benefit on getting a lead to your business. It play important role in increasing the page rank of the website.