Defects don't hide Yu. It's an allusion to Zhou Yu's spy hiding his flaws. Legend has it that Zhou Yu has a mole on his eyes, which grows on his eyes. When he opens his eyes, he can't see, but when he closes them, he can see. Once this Sun Ce found this problem and asked Zhou Yu. Zhou Yu is also very humorous, and he replied with great literary grace that "flaws don't hide Yu", which probably means that this mole can't hide his style.