Whom Can Tell One’s Social Class Based on Grammar?

From a New York Times opinion piece by Peter Coy headlined “Whom Can Tell One’s Social Class Based on Grammar?”:

Social class can be hard to discern when billionaires wear hoodies and work late into the night instead of dressing resplendently and lounging poolside like the wealthy of the past. But people are as obsessed by class now as ever, so we need to resort to other characteristics to tell who fits where.