[endgame]

I wasn't around at the time, but surely ASCII was (even if not ubiquitous)? Is there any particular reason that the FS/GS/RS/US (file/group/record/unit separator) characters didn't catch on in this role?

[EvanAnderson]

I did an ETL project years ago from a legacy app that used these delimiters. It was gloriously easy. No need to worry about escaping (as these characters were illegal in the input). It's a shame they didn't catch on.

[al_borland]

If I had to take a guess, I’d say the answer is as simple as there is no key for them on the keyboard.

[euroderf]

Sounds like a job for a macOS keyboard code whiz.