It's the same as whitespace. You don't expect it to be round-trippable, it's just to make the source file easier to read. Likewise I would interpret any expectation of the preservation of comments the same as an expectation of the preservation of whitespace: weird, unreasonable, and probably arising from a misunderstanding of how JSON works.
XML preserved whitespace, too! I dislike XML intensely, but there was a method to its madness. There’s a method to JSON, too: simplicity and usability.
You start adding things to JSON, you lose that.
It’s unfortunate how many APIs are documented with a single json example, but annotating them with comments (and maybe types?) would help immensely.