Each you perform an action regarding a WooCommerce order, a note is created. This is the best way to track every single action made on an order, and of course that’s very useful when your team needs to get the full order history. That can be also useful to share this order notes history to your customer. The best way to do it is to add the notes in the completed order email. What you need to know is that these notes are WordPress comments, so any WordPress comments related function can be used, and you can retrieve any data using the comment object.
Here what you can see in the administration, on the order edit page:
To display all these notes in the order completed email, simply add the following code to the customer-completed-order.php file. Please note that this file is a template; basically a custom template allows you to override WooCommerce default files and use your own custom files instead. Here is a quick tutorial that will explain you how to create your custom templates: http://docs.woothemes.com/document/template-structure/
So, create a folder called woocommerce in your theme folder. In this folder, create a new folder called emails, and in this folder duplicate the customer-completed-order.php from wp-content/plugins/woocommerce/templates/emails. And add this snippet at line 51:
Here is the result in the email: