The only one I really would avoid is passing things between or touching chopsticks together. This is reminiscent of Japanese funeral rituals and thus considered rude to do at the table.
The others are more about common sense and trying to help you enjoy the sushi as the chef intended:
They are bite-sized pieces, designed as a flavour combination, so don’t break them up in any way
If you don’t want rice, sashimi is a good way to get that
Putting too much soy sauce on the rice can make it fall apart
(real) Wasabi is delicate and mixing it with soy sauce will certainly destroy its subtle flavour. In any case in a high-end place the sushi chef will have added everything that’s intended as part of the flavour combination before serving the sushi, so adding stuff is not necessary
But again, these are suggestions. Enjoy the sushi how you like, you’re not hurting anyone.
The only one I really would avoid is passing things between or touching chopsticks together. This is reminiscent of Japanese funeral rituals and thus considered rude to do at the table.
The others are more about common sense and trying to help you enjoy the sushi as the chef intended:
But again, these are suggestions. Enjoy the sushi how you like, you’re not hurting anyone.