That guy's wrong about double-hyphens. That's historically been MLA and APA style for an em dash, and it's also an adequate substitute in cases where the full e

That guy's wrong about double-hyphens. That's historically been MLA and APA style for an em dash, and it's also an adequate substitute in cases where the full em dash is unavailable or when the software doesn't support extended characters. Sounds lame, but it happens. The company I work for has an e-mail provider that doesn't support extended characters at all. Dashes, curly quotes, ellipses — all of those turn to gobblety-goop. So we have to use alternatives. It's also worth noting that the em dash is used primarily for apposition, not simply as a pause in the sentence and not as a replacement for a conjunction.