At the Hay-Adams this fall, members of Washington’s diplomatic community gathered inside the historic hotel’s glass-walled loft, with its postcard views of the White House, for a conversation about fashion. About clothes and their place on the world stage. The program, hosted by the State Department and Elle magazine, included a panel discussion, in which I was invited to participate, that featured designer Derek Lam. When the conversation came around to first lady Michelle Obama — because how could it not? — Lam dropped his head in a mournful manner and lamented: Her departure from the East Wing signaled the...