They tend not to survive roundtripping well, for example. JSON describes data; comments are metadata. To do them well you'd have to bring them into JSON infoset

They tend not to survive roundtripping well, for example. JSON describes data; comments are metadata. To do them well you'd have to bring them into JSON infoset, such as it is. (ETA: JSON already has problems with canonicalization. Adding comments makes this worse. Are they in or out of the equivalence over JSON terms?)