Marketo is going to dedupe against email address.
What you can do is disable pre-fill on that form and page by turning that off on the Form level. This is what people call a Kiosk form. You will need to disable pre-fill on each Field.
By disabling pre-fill, will that prevent overwriting of previously submitted information connected to that user?
For example, if someone fills out the same form multiple times (using the same name/email address but with differing other information) will Marketo keep all of the info he submits or just the latest information?