* 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?
Comments: yes, I read Douglas Crockford's post on the matter. I guess I'm not genuinely worried about that, though, and my hope is that shipping a JS parser that works on both the client and the server will help standardize implementations from the start.
Special characters: sorry I didn't write a formal spec =), but the intent is to be a pure subset of ES5 just like regular JSON is a pure subset of ES3. Unquoted object keys in ES5 can contain only letters/numbers/_/$, and only begin with letters/_/$. So yes, '1hello' would need to be quoted, just like regular ES5.
I'm not sure how to respond to your why other than what I've already written. I never claimed this was the biggest problem we have. =)
JSON is not exactly tied to javascript. For example the number-type is not specified in much detail. You could imagine this to be a 64bit int but if you load it into javascript it will be converted to a double and you will loose precision if your number is big.
Anyway, I wouldn't focus on JavaScript engines because JSON is now a universal format so for languages other than JavaScript you will have to define a formal specification.
* 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?