It is actually from this Bruce deduces which the Joker would not treatment who Batman is; he only cares for Batman, and that to accept Batman's true id would spoil the Joker's "enjoyment". Bruce is later seen during the Batcave, Using the Joker's profile on-display screen, with "Id Unidentified" exhibited, https://zanderruvxz.bloguerosa.com/15760066/getting-my-sacasino-to-work