LONDON—Any veteran investor will tell you that financial markets overshoot when trouble hits, but what if that market is the world’s second-largest economy and the regime has decided the rules of the game have changed? The Chinese regime’s months-long regulatory clampdown has included big names in e-commerce, the gig economy, exam cramming and most recently online insurance. Close to $1 trillion in market value has been wiped off China Inc. since February. For big firms that also list on markets like Wall Street because it brings in international investment, 2021 is already the worst year since the global financial crisis. It could spring back of course, but there’s the rub. Many analysts are convinced things will settle, but only the Chinese regime’s ruling elite know if and when that might be. “Investors have been jolted,” said Paul O’Connor, head of multi-asset at Janus Henderson. “This will weigh heavily on the …