Three things:

* Comments in JSON files are not a great idea because people might (will?) abuse them to add special instructions for their own serializers. As soon as this happens we'll have a format that is not compatible with other serializers.

* JSON today is a universal format. So, what are special characters? Should '1hello' be quoted? If no, then its not a subset of JavaScript anymore. If you're writing a new specification you have to define all those things. Same with multiline strings: space after backslash?

* Why? I know that hand-writing JSON can be annoying but is this really the biggest problem we have?