Photo Illustration by Thomas Levinson/The Daily Beast/MaxAll around the Bat Cave in Harley Quinn, you’ll find details designed to remind you of the Bat Family’s one rule. The pillowcase, the WiFi password, and even the singing fish on the wall all want observers to remember that in this crew, “We Don’t Kill.”As reasonable an edict as that might be for a group of vigilantes, and as reformed as the Joker’s former sidekick has become, that demand proves difficult for our newly minted “hero.”When sh