Final answer:
When noticing a smudge on a plate, it should be rewashed in the kitchen rather than wiped off or ignored to maintain dining room hygiene and safety.
Step-by-step explanation:
If you notice a smudge on a plate, you should never just wipe it off with your cloth or ignore it because that could spread germs or debris, making the plate more unsanitary. The correct action is to take the plate back to the kitchen and rewash it with soap and hot water to ensure it is thoroughly clean before sending it to the dining room. This practice is in line with maintaining high standards of hygiene and ensuring the health and safety of diners.