Blog commenting is a great way to promote your MLM Blog. Sure, you can get a bunch of backlinks, but there is much more to it.
First, you will learn a lot from reading other blogs. You can learn things to help you in your business as well as get ideas for topics to write about on your blog.
You can even build some good relationships with other bloggers in your niche too. Networking with others is a powerful thing, as if you did not already know that thanks to the popularity of sites like Twitter and Facebook.
The biggest thing to keep in mind when commenting on blogs is to add value. Comments like, "Nice post" are not helpful to anyone. Most bloggers see this as spamming their blog and will remove your post.
On the other hand, if you leave good feedback, many bloggers will return the favor. This is helpful to you since having a lot of comments makes you look like more of an authority.