Rewritting the header means removing the submit button from the DOM, and losing the submit event.

Example:
* modify an input value
* click (with the mouse/touch) the Save button
* browser with submit 'change' event on the input and 'click' event on the button
* if 'change' event is triggered before, it will lead to the header rewrite. The 'click' event on the button will lead to a form 'submit' event, which will not be catched by the gadget, as the form is already outside the DOM