I don't wash my belt for the simple reason that my instructor told me not to. I don't believe that it will wash away my knowledge but I do believe that it is important to practice discipline (doing what you are told to do...or not to do) and it is important to show respect for your instructor. Different people train for different reasons but for me, I still like to train in schools that practice discipline and respect. For those of you who train for the sole purpose of learning to fight, I respect your opinions as I have trained in fighting schools where etiquette was pretty much thrown out the window. Belts were often thrown on the floor, belts were washed, etc.) I respect these schools for their purpose (strictly learning to fight). I don't think that one type of school is better than the other, it all depends on your personal reason for training.