The Federal Housing Finance Agency has concluded that accepting incentive payments from the U.S. Treasury for writing down loan balances on certain Fannie Mae and Freddie Mac mortgages could end up saving taxpayers money, but the agency is not ready to make the controversial change in policy for the two government-sponsored enterprises. What’s holding the FHFA back is the unresolved concern that forgiving principal on GSE loans will encourage unknown numbers of underwater Fannie and Freddie borrowers to deliberately stop making payments or claim hardships so they can get their debt reduced. A...