More generally than editor support, how is the average person expected to type them? I could easily add them to my keyboard, but if "editor support" turned out to mean "Edit > Insert > Record Separator Character" and I was now bound only to editors that support this, absolutely nobody is going to bother. They specifically need to be trivially typable in exactly the way commas and newlines are.
Realistically I don't think anyone (at least on HN) would presume that editor support would be so weirdly obtuse, but it's not exactly well-defined here, either.
I'm mostly just thinking out loud, here, not really critiquing anyone.
Actually, there is already a standard way for someone to type these with the control key. To be specific, they are:
FS: ^\ GS: ^] RS: ^^ US: ^_
Since these delimiters are not much used, on many terminals ^\ is mapped to send SIGQUIT. Use 'stty quit undef' and you can then type this at the keyboard. This works on Linux and OS X, and likely most other systems. Note that with most keyboards you are also using shift for RS and US. For emacs, prefix with C-q so that it inserts the literal.
Other posters have noted that they have ASCII separators recently, I have as recently as 2018 internally at a FAANG. So they are not completely unknown in the wild.
which modifier would that be, Alt/Ctrl or Cmd? Also there is a chance that this combo will not work on some platforms, some may already be in use as a hotkey.
Realistically I don't think anyone (at least on HN) would presume that editor support would be so weirdly obtuse, but it's not exactly well-defined here, either.
I'm mostly just thinking out loud, here, not really critiquing anyone.