Why not JSON for simple configuration files?

JSON is an ideal format for REST APIs and other forms of data intended for machine exchange and it probably always will be because:

• It's a simple spec.
• It has all the basic types which map on to all programming languages - number, string, list, mapping, boolean and no more.
• Its syntax contains a built in level of error detection - cut a JSON request in half and it is no longer still valid, eliminating an entire class of obscure and problematic bugs.
• If pretty-printed correctly, it's more or less readable - for the purposes of debugging, anyway.

However, while it is eminently suitable for REST APIs it is less suitable for configuration since:

• The same syntax which gives it decent error detection (commas, curly brackets) makes it tricky for humans to edit.
• It's not especially readable.
• It doesn't allow comments.