A problem exists in earlier versions of Acrobat/Reader when using rich text fields within an XFA Form. If the user deletes text from a rich text field; saves the form; and then closes it; when they reopen the form the original text will be restored to the rich text field.
This is obviously not ideal or expected behaviour.
One workaround is to loop through the form and reset ONLY rich text fields that are null. This seems to address the issue.