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.
I was taught to pass food with the back end of the chopsticks, not the part that goes in your mouth. Is that your understanding as well?
Generally, if you want to pass food to someone, put it on a plate so they can pick it up themselves.
The only reason to use the back of the chopsticks, is if there is a shared plate of food in the center without a separate set of serving chopsticks. Taking from the shared plate with chopsticks that have been in your mouth could be considered unhygienic. You can use the back of the chopsticks to move the food to your own plate, then eat it.
However this is more like advanced etiquette and not a crucial rule, in my opinion. The only really bad things to avoid are sticking your chopsticks upright into rice and passing food between chopsticks.
Wait, you don’t pick it off the leaf on the person, and put it directly in your friend’s mouth?
