[WooCommerce BR] Restrict coupon from being used bt its author

functions.php

<?php
add_filter('woocommerce_coupon_is_valid', 'wcbr_coupon_is_valid', 10, 2);
function wcbr_coupon_is_valid( $valid, $coupon ) {
    global $woocommerce;

    $customer_id = $woocommerce->customer->get_id();

    $coupon_author_id = get_post_field( 'post_author', $coupon->get_id() );

    if ( $customer_id === $coupon_author_id ) {
        return false;
    }

    return $valid;
}