SHANGHAI, Dec 12 (Reuters) – JD.com, one of China's largest e-commerce firms, pledged 22 billion yuan ($3.12 billion) in housing support for its army of couriers, as competition intensifies in the instant retail market. JD.com's move, announced in a post on its official WeChat account on Friday, follows a similar promise from food delivery firm Meituan. Last month, Meituan said it would invest 10 billion yuan over the next five years to build a more comprehensive welfare system for its delivery riders. JD.com and Meituan, along with Alibaba, have this year been locked in a battle for market share in the instant retail space, which refers to goods delivered within one hour. This rivalry has pushed companies to allocate billions of dollars toward consumer subsidies and discounts, squeezing p

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