1. I have seen Japanese people do approximately half of the things on the list.

2. The two listed as "serious" are related to Japanese funerary rites, and so are clearly culturally specific.

3. Several of the things listed are perfectly acceptable in other chopstick-using cultures. Many are also perfectly acceptable to do with a fork and/or knife in cultures that use forks and knives. I think I would go so far as to say that there is not a single thing on there for which it would be widely considered rude to do in all cultures.