To this day I am baffled why choose YAML? Personally, I think its more error prone, less flexible, and harder to read than JSON. Not to say JSON is a perfect format, but it sure feels better than YAML.
JSON is a terrible config format, and an ok data interchange format.
But maybe I misunderstood. Can you give an example of a comment that makes sense / is required in a configuration JSON?
Mostly because I don't know whether the person customizing my code will read the README, but they'll definitely see the comments I wrote right before the configuration option itself.
With comments and some extra whitespace, they can go through the file line by line, read what a specific option does, configure it properly, and move on to the next one. No back and forth to the README required.
Something like http://www.relaxedjson.org/ is a JSON we need. An implicit root object would make it almost perfect for writing configuration.