We’ve enabled the Disable Comments plugin on all WordPress blogs.
This plugin allows site administrators to globally disable comments on any post type (posts, pages, attachments, etc.) so that these settings cannot be overridden for individual posts. It also removes all comment-related fields from edit and quick-edit screens.
How to use
When you log into your WordPress site, you will notice this:
Click the link it presents for configuration page. Check these boxes and save configuration:
How to change settings
If you need to change a setting or you can no longer see the link to configuration page, you can get back to the Disable Comments plugin settings by going to Settings > Disable comments.