I think it's mostly a cultural thing -- the clapping. If I lived in Italy, I'd be happy to join in and praise a film in the cinema if I liked it. Italians are such a loving and passionate bunch that it's easy to take over their habits. And as you said, filmmaking has a history in Italy. But if you were to clap in countries like the UK or US, people would be looking at you strangely, thinking you're a weirdo.

I also agree that when the actual filmmakers are present after a screening, it makes more sense to applaud them and their effort of showing up and doing a Q&A for instance -- besides their film which probably took a lot more to make.

Other than all that, you're totally right and I agree with most of things you cited here.