Princess Diana, Shakespeare, and Anne of Green Gables were INFPs. Jesus and Gandhi were INFJs, and so is J.K. Rowling. Barack Obama is probably an ENFJ, and Donald Trump is unmistakably an ESTP (in the company of Britney Spears and Madonna, might I add). So what do these four-letter acronyms represent, and why is everyone so eager to share them on dating sites, through social media, in the workplace, and — as I have done — on their blog’s “About Me”? These letters refer to a system of personality typing known as the Myers-Briggs Type Indicator (MBTI), one of the most widely used personality inventories popularized by laypeople and mental…