In my opinion, JSON works well for data interchange, but it's overused for configuration, it's not localization-friendly, and it's too syntactically noisy. INI is simple but lacks hierarchical structures and doesn't have a formal specification. Confetti is intended to bridge the gap.
I aim to keep Confetti simple and minimalistic, while encouraging others to extend it. Think of it like Markdown for configuration files: there's a core specification, but your welcome to create your own variations that suit your needs.
I'd take Prolog without I/O and (some? all?) extra-logical predicates as configuration language. Maybe if there's a way to require recursion to terminate, that'd be great, but not essential.