Hey, thanks for taking the time to read and commenting! :)

Problem #1 (at least for the "advanced" part of the article's suggestion) is unfixable unless you boil the ocean and change the POSIX spec. I tried to make that clear in the prose, but might have failed at it. It's also the reason why I chose the title to refer to `bash` scripts in particular.

Problem #2 becomes less relevant once you realize that problem #1 completely overshadows it. And in `zsh`, where you can also redefine `:` to invoke a custom function, tests via `[[` also work just like they do in bash.