Test the package with older versions of Python and support the oldest version that the libraries support, or at least the versions that come pre-installed in common OSes.

When the user has modified the default configuration in the config file, the package should print a message suggesting them to submit the changes as an issue if they think they'd be relevant to others.

This helps make the program better for everyone.

Nested selections are when a selection appears between a message value:

nested = You have { $apple-count ->
    [zero] no apples
    [one] one apple
    *[other] $apple-count apples
}.

unnested = { $apple-count ->
    [zero] You have no apples.
    [one] You have one apple.
    *[other] You have $apple-count apples.
}

Nested selections aren't supported because it may confuse GPT.

When translating files, the package should print an error and exit early when it encounters a nested selection.

This limitation should also be documented in the README.