Removes the word "private" and "protected" from the posts title.

remove-private-title-prefix.php

<?php
/**
 * Remove Private and Protected Title Prefix
 * @package     RemovePrivateAndProtectedTitlePrefix
 * @author      Bernhard Kau
 * @license     GPLv3
 *
 * @wordpress-plugin
 * Plugin Name: Remove Private Title Prefix
 * Plugin URI: https://kau-boys.de
 * Description: Removes the word "private" and "protected" from the posts title.
 * Version: 0.1
 * Author: Bernhard Kau
 * Author URI: https://kau-boys.de
 * License: GPLv3
 * License URI: http://www.gnu.org/licenses/gpl-3.0.txt
 */

/**
 * Remove the "Private" and "Protected" prefix from headlines
 *
 * @param string $content Text displayed before the post title. Default 'Private: %s'.
 *
 * @return string
 */
function remove_private_and_protected_prefix_title_format( $content ) {
    return '%s';
}
add_filter( 'private_title_format', 'remove_private_and_protected_prefix_title_format' );
add_filter( 'protected_title_format', 'remove_private_and_protected_prefix_title_format' );