functions.php

<?php

/**
 * vpm_comments_template
 *
 * Load our own template file for WooCommerce reviews
 */
function vpm_comments_template( $template ) {
	global $woocommerce;
	$comments_template_path = get_stylesheet_directory() . '/woocommerce/single-product-reviews.php';

	if ( get_post_type() == 'product' && file_exists( $comments_template_path ) ) {
		return $comments_template_path;
	}

	if ( get_post_type() == 'product' ) {
		return $woocommerce->comments_template_loader( $template );
	}
}
add_filter( 'comments_template', 'vpm_comments_template', 100, 1 );