Hong Kong’s move to mandate the use of its Covid-19 contact-tracing app at government buildings amounts to differential treatment, the city’s equality watchdog chief has warned, urging staff to rely on “common sense” in certain circumstances. But the new rule stopped short of breaching the city’s anti-discrimination laws, said Ricky Chu Man-kin, chairman of the Equal Opportunities Commission, in response to concerns it was unfair on those who did not own smartphones. “I think the way to go about it is to use common sense to deal with the matter effectively,” Chu told a radio programme on Saturday. The comments…