Always wondered if it is a flavor mismatch or a bad chemical reaction
Here's a short article on the debate but I'm a believer of "if it tastes good do it" :
I agree. I make stuffed clams oreganata every Christmas eve (basically Lidia Bastianich's recipe) - the stuffing includes parm. Also, when I make spaghetti alle vongole at home, barbarian that I am, I love it with a little fresh grated parmesan on top.
It's an Italian cultural thing. There are some exceptions but very few.
I don't think its anything like chemical reaction. Its just two flavors that do not marry. With a seafood pasta, you'd want some zesty/citrus feel to it, not so much the cheesyness on top. Then again, taste differs. Some people might love their seafood pasta with cheese. But most foodies will consider it a big NO NO, just purely taste wise.