The Chinese Communist Party is no fan of cryptocurrencies. Ten regulators have piled on in the People’s Republic, explicitly declaring all crypto activity to be illegal. It underlines the shortcomings of the asset class, but also – unintentionally – some of its appeal. Beijing’s ongoing crackdown is partly about curtailing capital flight via digital assets, perhaps a heightened risk right now because of worries about losses at property group China Evergrande. It’s also about financial stability, a concern even in, say, the United States. Cryptocurrencies are less useful if using them makes people criminals. The market reaction, a fall in...