Fannie Mae and Freddie Mac announced this that week that they will rely on mortgage sellers to make sure all the loans sold to the government-sponsored enterprises starting next year will be “qualified mortgages” that meet the controversial limit on points and fees. Some aspects of the QM standard will be easy to quantify and meet, such as maximum loan terms of 30 years and no interest-only payment plans. The 43 percent cap on debt-to-income ratio that’s part of the ability-to-repay rule issued by the Consumer Financial Protection Bureau will be waived for the GSEs. The stickiest wicket is...