[dragonwriter]

> Isn't this what parenthesizes are meant for?

Parentheticals (including non-restrictive appositives) can be set off in English by either commas, em-dashes, or parentheses. There aren’t a lot of hard and fast rules for which is used where, though a common (partial) rule is for appositives without internal commas to be set off by commas and thise with internal commas to be set off with em-dashes. This obviously leaves open the handling of non-appositive parentheticals.

There are other uses of em-dashes, some of which softly overlap with other punctuation—I’m not aware of any common alternative to two em-dashes for ommission of partial words (useful in transcribing unclear sources, for instance.)

> I don't understand what the issue even is here, and the RFC also doesn't clearly outline it.

The RFC—fake, the maximum RFC number currently is 9945—is a joke.