I use the new version 1.3.7 and allways my email was set to txt format.
Now i changed it in configuration to sent emails in MIME html format. It works OK but there are no payment details in the MIME html format when moneyorder payment module is used.

It seems that only the MODULE_PAYMENT_MONEYORDER_TEXT_TITLE is being sent to the customer in MIME html format but not the:
MODULE_PAYMENT_MONEYORDER_TEXT_DESCRIPTION
and the
MODULE_PAYMENT_MONEYORDER_TEXT_EMAIL_FOOTER.
that contain the payment details.

Seems like something is missing in the includes/classes/orders.php

When i change the settings back to only txt emails this information is being sent...