If I got a fridge with a freezer above the probe in the fridge would shut the power off at the set point. Thus the freezer would also be shut off. Exactly at what temp is unknown. Its unlikely to be useable as a full on freezer, it might get cool enough to keep Wyeast or bottled beers or it may just be a empty space not really useful for anythjng.
But if I get the appliance cheap or free that wouldn't matter. As long as the controllable section is big enough for the fermenter.
So I think a comb wouldn't be problematic. Though I still have to find one.