[rwmj]

What does "keep my scripts honest" even mean? Just use bash and don't make everyone else boil your ocean.

It's like saying you'll never use any Linux feature except those strictly defined by POSIX.1. Why would you do that?

[chasil]

Android uses mksh. If I write a script that uses read -p to present a prompt, it will fail on Android because it means coprocess on mksh.

The fundamental reality is that GPL does not run on iOS or Android (in userland). If you want to run scripts on those platforms (and they are ENORMOUS), then you cannot use bashisms.

Full stop.