Why do we keep having the "comments in JSON" discussion? Just use YAML.

json-with-comments-in.yaml

{
  # this is a comment
  "a": "hello", 
  # this is another comment
  "b": -1, 
  "c": [
    true,
    "test",
    null
  ], 
  # yet another comment
  "d": {
    "x": 1,
    "y": 2 
  }
}

plain-old.yaml

# this is a comment
a: hello
# this is another comment
b: -1
c:
 - true
 - "test"
 - null
# yet another comment
d:
 x: 1
 y: 2

May have to copy this idea!

:)