Add own HTML for Customer order note

customer-order-note-html

/**
 * Add the code to your theme functions.php file
 */

// Remove the order meta function from the email
remove_action( 'woocommerce_email_order_meta', array( WC()->mailer(), 'order_meta' ), 10, 3 );

// Add your own order meta function
add_action( 'woocommerce_email_order_meta', 'woo_add_order_notes_to_email', 10, 3 );
function woo_add_order_notes_to_email( $order, $sent_to_admin = true, $plain_text = false ) {

	// If you want to send those only to the Admin
	if ( ! $sent_to_admin ) {
		return;
	}

	// Get the order note
	$customer_note = $order->customer_message;

	echo '<h4 style="font-family:Arial,sans-serif;font-size:120%;line-height:110%;color:red;">Order Notes</h4>';
	echo '<ul class="order_notes">';
	if ( $customer_note ) {
		echo '<li class="customer-note note">'. $customer_note .'</li>';
	} else {
		echo '<li class="no-order-comment">There are no order notes</li>';
	}
	echo '</ul>';
}