Disable Comments is a very good plugin for disabling comments. This plugin allows you to globally disable comments on any post type. If you install Disable Comments on a multi-site site, you will disable all comments on the entire network.
You can choose what to disable:
All “Comments” links are hidden from the Admin Menu and Admin Bar;
All comment-related sections (“Recent Comments”, “Discussion” etc.) are hidden from the WordPress Dashboard;
All comment-related widgets are disabled (so your theme cannot use them);
The “Discussion” settings page is hidden;
All comment RSS/Atom feeds are disabled (and requests for these will be redirected to the parent post);
The X-Pingback HTTP header is removed from all pages;
Outgoing pingbacks are disabled.
If you don’t want anybody to comment on your site, Disable Comments really a must-have wordpress best plugin! It is really easy to use and works flawlessly.