The benefits of encouraging blog comments can be positive and far reaching. From the perspective to keeping the site lively and interactive blog comments are the dominant force in producing such an environment.
When a site has the constant exchange of comments there will be a steady flow of interest in the site or blog because the people involved in the commenting would want to view the responses to their comments.
This also applies to those visitors who are not physically participating in the commenting process, but are only interested in viewing the comments. Therefore the high traffic drawn to the site would be an important benefit.