Well unfortunately the bug here is that if you press the button "SEND MAIL" on hold, pending or processing order you will see your last order comment marked as "Customer Notified". This message is false because the customer isn't notified.
We test it in real environment and the bug seems to be at Magento ver. 1.9.3.10 and Magento ver. 1.9.3.9.
Any idea how we can fix that false "Customer Notified".
