If your wrist is making unnecessary marks even if the Write Protection mode is on, please try the following:
Please disable the 'multitasking gestures' from your iPad settings' app. This needs to be done in order to rest your wrist on the iPad screen when taking notes in Noteshelf (or any other note taking app). Apple did not provide a way for us developers to workaround this issue.
Also, check if you have the "Zoom" option in the "Accessibility" settings turned on (again from the iPad settings app). Disabling this should resolve any issues with wrist protect mode. This setting also conflicts with the multitouch capabilities of iOS apps.