When you’ve allowed comments on your blog, try to make it easy for people to leave a comment. remember, each field that has to be filled out besides the comment box, name and email, will cut your comments significantly. Take out captcha and try to let Akismet do the moderation for you. Keep it simple for people.
Maybe even use a universal comment system, like Disqus or LiveFyre, Jetpack Comments, Google+, or even Facebook comments. These systems also encourage comments and social shares and make moderation and management a breeze.