Don't worry, I wouldn't do things like this in JSON. Nevertheless, it can be very useful to have comments along with configuration values, for example to explain the actual values (not their purpose) and why they were chosen. That's information you can't add to the code which processes the values.
json with comments can be parsed by a yaml parser. It's how I write yaml, in fact (yaml is a superset of json. any valid json is valid yaml, but it also supports comments)