This snippet comes in handy if you want to disable comments on attachment pages, got lots of media already and don´t want to go through each single one (no bulk edit here unfortunately). Credits: http://premium.wpmudev.org/blog/wordpress-comments-off/ Goes to Dynamik Custom - Functions

no_comments_for_media.php

//* Don´t allow any comments on media attachment pages
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 );