Bare fingers can be polite. At a sushi counter, picking up nigiri with clean hands follows an accepted dining custom, while rubbing disposable chopsticks together can suggest that you expect splinters from inferior utensils. The difference is respect. One gesture suits the food; the other can look like a public inspection of what your host has supplied.
Your hands are not cheating. Nigiri combines a slice of fish or another topping with a shaped portion of seasoned rice, which can fall apart if you squeeze it awkwardly between chopsticks. Fingers offer gentle control. You can lift the piece without crushing the rice, and, if dipping it, turn it so the topping rather than the rice touches the soy sauce. Chopsticks are welcome too. This permission does not extend automatically to every dish: sashimi, served without the rice base, is generally eaten with chopsticks rather than fingers.
The rubbing carries different baggage. When you scrape the separated wooden sticks against each other, the implied message may be that the restaurant has provided rough, poorly finished utensils requiring repair before use. Context still matters here. Not every diner intends an insult, not every host takes offense, and a genuine splinter is a practical problem rather than an etiquette puzzle. Skip the sanding performance. If a stick is visibly damaged, ask quietly for another pair instead of treating the whole table to the repair job. Why criticize utensils before dinner?
