It is curious that mainland companies listing in Hong Kong enjoy more latitude in making board appointments here than at home. If the stock exchange has its way, that will change by the end of next year, when at least one third of a firm’s directors will be independent, bringing the city into line with the mainland, though still not with Singapore, the United States and Britain. The exchange also wants companies to ensure that all directors, including the city’s best-known tycoons, have eight hours of training every year, and to limit the number of boards a person can serve on to avoid them spreading themselves too thin.