bp_get_the_thread_message_alt_class()

	function bp_get_the_thread_message_alt_class() {
		global $thread_template;

		if ( $thread_template->current_message % 2 == 1 ) {
			$class = 'even alt';
		} else {
			$class = 'odd';
		}

		/**
		 * Filters the CSS class used for message zebra striping.
		 *
		 * @since BuddyPress 1.1.0
		 *
		 * @param string $class Class determined to be next for zebra striping effect.
		 */
		return apply_filters( 'bp_get_the_thread_message_alt_class', $class );
	}