There is a stark contrast between the PBOC and the US Federal Reserve’s approach to managing markets. The Fed tends to treat investors like the recently burgled: reassurance at every stage, no loud noises during the night. American central bankers have been signalling for two years that the crisis-era programme of vacuuming up bonds from the market, known as quantitative easing, would be wound up as the economy improved. ... China’s abrupt interventions have therefore come as a surprise to investors who have only recently gained direct access to the country’s A-share market. By Friday night, after five days of...