As concerted state buying puts a floor under mainland China’s onshore stock market amid Beijing’s stabilisation measures, investors in Hong Kong worry about coping with high volatility at a delicate time, with multiple market-roiling factors. These include geopolitical tensions, sluggish earnings growth, a stumbling artificial intelligence trade, possible US tightening and a looming supply glut from expiring share lock-ups. Investor worries also grew after renewed military strikes in the Middle...