Not something I'd add to the code, but you could probably implement it with some custom JS.
I remember now what I was doing when I commented that code out, I was actually looking at some potential ways to allow user rating on a new form. But turned out that it's quite a lot of work, so I punted on doing it, I just forgot to uncomment that check for new record.
Basically, it would have to have a check on form load, and if new form and user rating enabled, disable the AJAX rating method, and instead add a onAfterProcess hook to retroactively add the #__fabrik_rating table entry from the submitted rating value, once we know the PK of the form.
But for now, the easiest way is just to rate it in the list, when you return to list view after submitting the form.
-- hugh