Lately, I have been encountering more and more restaurant goers who vigorously rub their wooden chopsticks together before using them. Some people rub so vigorously, they seem like they are trying to start a fire. I find it a bit disconcerting when the person next to me at a sushi bar or yakitori bar is doing this.
So why do people rub their chopsticks together? When I first went to Japan, I was taught this was grossly rude, very uncouth. Was I given wrong information? Is it considered perfectly polite to rub your chopsticks? And does it serve some purpose? (I've never personally encountered a splinter on my chopsticks that required me to rub them together to remove the splinter).