People always crawl out of the wood-work swearing blind they've always used em-dash, but the truth is that actual em-dash usage has exploded by a factor of thou

People always crawl out of the wood-work swearing blind they've always used em-dash, but the truth is that actual em-dash usage has exploded by a factor of thousands and is therefore, along with other markers, a strong indicator. It's not proof, it is evidence.