While logged in, click "My Profile" in the top navigation menu and click on "More Options" which makes an array of options available for you to toggle. The third option down from the top is for enabling/disabling comments on your blog posts. If you do not want other users to be able to comment on your blogs, toggle the slider off by clicking on it. You can enable comments again at any time by clicking the toggle again.
Ask me to find out... Tantra