Two chopsticks standing in a bowl of rice mirrors incense at a funeral. It's a strong taboo across Vietnam.
When you pause mid-meal, rest your chopsticks across the top of your bowl or on the provided chopstick rest. If neither exists, lay them flat on a napkin or on the edge of a small plate.
Also avoid passing food chopstick-to-chopstick — that mimics funeral bone-passing rituals. Place items on someone's plate or bowl instead.