On Jan. 30, the affluent town of Hillsborough held a city council meeting to discuss its floundering housing element plan. The plan, which lays out how towns and neighborhoods will meet state-mandated housing targets within eight years, was supposed to be submitted to California’s Department of Housing and Community Development by Feb. 1. It wasn’t. And it remains in limbo more than a week later. More troublingly, a Hillsborough resident proposed a loophole that’s been popping up in other affluent Bay Area towns trying to meet their housing requirements: build a segregated development specifically for developmentally disabled adults, thus preventing...