The debate over stablecoins has come a long way since Facebook announced the creation of Libra (now Diem) almost exactly two years ago. An obscure corner of the digital sphere that was poorly understood then is now subject to increasingly intense scrutiny by central bankers, regulators, and investors. The stakes, including for financial stability, are high. Market capitalisation, or circulating supply, of the four leading US dollar stablecoins alone exceeds $100 billion.

But more intense scrutiny does not mean better understanding. Start with the belief that stablecoins are intrinsically stable b...