A) Wat. B) Somebody's gotta write those serialization libraries, and they probably do a fair amount of string manipulation to do so. C) You can't .join data s

A) Wat. B) Somebody's gotta write those serialization libraries, and they probably do a fair amount of string manipulation to do so. C) You can't .join data streams without buffering, which defeats the purpose. D) Adding commas on a preceding line every time you add a new item to a list can pollute diffs. E) Trailing commas are syntactically correct in ECMAScript 6, and supported by a fair few other languages.