Regarding the "clearit" approach:
"Please be aware that if you're using default values on fields you've defined as required, they will validate even if the user doesn't not populate them or change their value. This is due to the fact that the default value will be submitted as the form field value if they are not changed by the user."
Surely this isn't an answer ... is there not a way to check the fields for the "Default Value" upon submit and make sure that the Placeholder text is not validated against?