Colin Dickey writes for Hazlitt about the practice of covering mirrors after a death:

There seems to be no universal reason behind the custom. Reginald Fleming Johnston, documenting this practice in China in 1910, claimed that the reason mirrors are covered is because “if the dead man happens to notice a reflection of himself in the glass he will be much horrified to find that he has become a ghost, and much disappointed with his own appearance as such.” Johnston also notes that for some, there is a belief that “every mirror has a mysterious faculty of invisibly retaining and storing up everything that is reflected on its surface, and that if anything so ill-omened as a corpse or a ghost were to pass before it, the mirror would thenceforth become a permanent radiator of bad luck.”