Coles’s “Down Down” promotion is one of Australia’s best known campaigns. But the supermarket has been caught red-handed after a federal court judge found Coles misled shoppers by promoting fake discounts . Through its proceedings, Australia’s competition regulator has given consumers an intriguing look-behind-the-curtain moment, exposing how a major supermarket sways shoppers to buy its products. Here’s how the case unfolded. Faulty ‘guardrails’ In a ruling delivered on Thursday morning accompanied by a 523-paragraph judgment, justice Michael O’Bryan explained how Coles tripped itself up when trying to ramp up its well-known campaign. The Down Down promotion, known for its catchy jingle and large red hand, relies on a practice called “was/is” comparative pricing that claims a product is cheaper than it used to be. This promotional tactic has been scrutinised by the Australian Competition and Consumer Commission at Coles and other retailers.…