I think the real loss here is that with a # or // the person reading the file immediately knows this is a comment. This line won't be read by the interpretor, and it's purely here for me to read it, so I probably should do.

The following however

    {
      "comment": "Some comment",
      ...
    }

Suddenly I'm not sure if this is meant for me, or if it's actually a configurable state without going into the program itself and checking if it uses it.