China unveiled broad regulations Wednesday that ban major platforms such as Alibaba Group Holding Ltd. from coercing online merchants into promotions, one of a raft of new measures intended to cool rapidly intensifying e-commerce competition.The guidelines take effect February and follow a series of notices from Beijing warning Alibaba and rivals including Meituan and JD.com Inc. against pressuring merchants into discounts and other measures accused of disrupting market order. A separate set of ...