Cacher is the code snippet organizer for pro developers

/* ------------------------------------------------------------------*/
/* ADD BBPRESS PRIVATE SHORTCODE */
/* ------------------------------------------------------------------*/
function remi_bbp_shortcodes( $content, $reply_id ) {
	return do_shortcode( $content );
}
add_filter('bbp_get_reply_content', 'remi_bbp_shortcodes', 10, 2);
add_filter('bbp_get_topic_content', 'remi_bbp_shortcodes', 10, 2);

function remi_add_bbpress_private_shortcode( $atts, $content = null ) {
	if( !current_user_can('administrator') ) {
		echo do_shortcode( '[alert type="warning"]This content is private[/alert]' );
	} else {
		return '<span class="alert-message notice">'.$content.'</span>';
	}
}

add_shortcode("private", "remi_add_bbpress_private_shortcode");