[jauntywundrkind]

JSON5, JSONC, and others have comments.

Also, there's the old dirt hack

  {"item": "this is a comment",
  "item": "//so is this but more obvious",
  "item": "because in 99.99% of implementations, last value wins:"
  "item": 42}

[bvrmn]

It's kinda important to keep comments on automated transformations.