I always meant to use hjson somewhere, but never managed to. YAML is so complicated, and JSON is almost fine, except for: no comments, no multiline strings. Quoting keys is tedious but not terrible. Personally I don't mind quoting string values at all.

There are places with slightly relaxed JSON, like JSON + comments (e.g. https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...). But it's often not well documented, and because these relaxations lack a name there's no commonly accepted set of relaxations.

But I guess we should just accept YAML, as it seems to be the standard-that-isn't-json.