By default the front page of the blog is the page all Posts are displayed on. It's the posts when displayed on their own pages after your click a post title or comment link that you disable or enable comments on, and not the dynamic page where posts are only showcased.
This page > Settings > Discussion
Discussion settings is where you set up defaults for comments.
We can also override the default settings and enable or disable future comments on any individual post or page.
Note: By default, new blogs on WordPress.com will have the Discussion hidden. You can reveal it by clicking on Screen Options http://en.support.wordpress.com/screen-options/ on the top right corner of your Admin page, and checking the box that says Discussion so the module is included. http://en.support.wordpress.com/modules/#list-of-modules
You go to Pages > All Pages, hover over the page title, click Quick Edit, uncheck the option "Allow Comments", click Update. That's all. http://en.forums.wordpress.com/topic/remove-comments-section-and-posting-format?replies=6