Hi,
Awesome! This is great starting point, but as you stated there are some issues, here's couple of them:
*You cannot anymore remove the green tick from the message from the customer (=> Fatal Error) - minor issue, but still
*As you stated it doubles the messages that are in both tables
*It collects ALL the message with that customer, not just the ones related to that order
BUT it's still huge improvement compared to the removed functionality that Prestashop team has done.