Disable Comments, another WordPress plugin allows administrators to globally disable comments on their site. Comments can be disabled according to post type.

Remember:

Use this plugin if you don’t want comments at all on your site or on certain post types. After activating it, plugin settings can be accessed from the ‘Settings’ menu in the administration area.

Related Plugin:

Read this article to Disable Comments By Default On New WordPress Pages And Custom Post Types.

You can easily disable comments by default on new pages and custom post types, with the ability to individually set them on a page or post basis.

By default, WordPress provides you two options:

1. You can have them active by default.
2. You can either disable comments and trackbacks by default for all pages and posts.

WordPress doesn’t provides you any specific setting that allows comments and trackbacks to be active by default for posts, while disabling them on pages or any other post type but using No Page Comment plugin you can have these options also. Simply install, activate it then visit its options from Dashboard->Settings->No Page Comment.

You can very easily disable comments on WordPress media attachments. Open your theme’s function.php file and add the following hack:

function filter_media_comment_status( $open, $post_id ) {
$post = get_post( $post_id );
if( $post->post_type == ‘attachment’ ) {
return false;
}
return $open;
}
add_filter( ‘comments_open’, ‘filter_media_comment_status’, 10 , 2 );