Facebook followers were eager to see what CEO Mark Zuckerberg chose to wear to testify before Congress Tuesday —a clue into how he perceived the event and how he wanted to be perceived. When building his company, the 33-year-old billionaire famously favored T-shirts, hoodies, jeans and sneakers—a schlubby-collegiate style that infuriated some who saw him flouting traditional business wear.
However, over the years the Facebook chief has shown he can dress up when the occasion—and the institution—calls for it, such as a visit...