If any more leaders of finance want to warn about the imminent bursting of the private credit bubble, they will have to get in line. Jamie Dimon, the always opinionated head of JPMorgan Chase, has spoken of “cockroaches” in the system, which allows asset managers to make huge, lightly regulated loans to corporations. Danny Moses, who predicted the 2008 financial crisis in “The Big Short,” has warned that the flood of nonprofessional investors entering the market reminds him of the run-up to that crash, while UBS raises the possibility of the default rate hitting an alarming 15 percent.