Douglas Crockford wrote:
"I removed comments from JSON because I saw people were using them to hold parsing directives, a practice which would have destroyed interoperability, writes Douglas Crockford, who popularized the text-based data format."
The following example JSON stores the name and age values with the _comment key which is used for commenting.
"name": "Rohatash", "age": 35,
"_comment": "This is a comment",
Here _comment Key can be treated as comment.