Custom Column in edit-comments.php list table

[wordpressplugindeveloper]

class-wp-ms-sites-list-table.php, class-wp-media-list-table.php, class-wp-posts-list-table.php and other list table php files they do have a columns hook such as apply_filters( 'manage_posts_columns', $posts_columns, $post_type ); in get_columns method.

But why class-wp-comments-list-table.php is not favored?

[scribu]

All the list table columns pass through a filter called in get_column_headers():

​http://core.trac.wordpress.org/browser/trunk/wp-admin/includes/template.php#L224