But one of the more interesting ones is the horror expressed by natives at the prospect of cheese and fish together. Even I, who am undistinguishable from an Italian in every way (appearance, accent, background) had to be told many years ago by an Italian waiter (and they generally are not snooty, like some nationalities I could mention): signora, non si mette il formaggio sul pesce (one does not put cheese on fish, ma'am). He looked very serious as he was saying this.
After this scolding, I mended the error of my ways. To the point that making spaghetti with clams or a fish risotto (among my very favorites) with cheese is unthinkable.
I do feel that any self-respecting rule will have its exceptions. I remember the best potato skins I ever tasted at the now-defunct Fishery in Cambridge (Mass.). With shrimp and cheese (cheddar?). And they were Mediterranean folks, too (Greek). But generally I do think that this is a taboo with a strong basis in truth. Not scientific, but esthetic.
Some invisible parm/
Lurking in your clams?/
Who you gonna call?/
(in the photo, an anthropomorphic fresh mozzarella trying to ruin some oysters)