I've set up CiviPetition. Just to test, I've added Subject and Details to an activity profile as well as a field from a custom fieldset for this petition.
When I visit the Sign page (as a logged in user) I see that the subject and details are pre-populated with values from some random activity (not even an activity of the petition type, but at least it is one that belongs to my contact record). Why is that? Why is the form not blank?