Hong Kong Exchanges and Clearing (HKEX) is on course to deliver its best earnings report card, after a surge in stock listings and trading volume. The challenge of sustaining that momentum to justify its high-flying stock price awaits its new boss.The city’s stock exchange operator probably earned 22 per cent more profit, at HK$11.4 billion (US$1.47 billion) in 2020 or HK$8.99 per share, according to a consensus among analysts polled by Bloomberg. This would be the highest since it went public…