Instead of inventing "JSON with comments" format, why not simply use JSON5?
Having a mess where JSON parsers sometimes do, and sometimes don't allow comments is a bad outcome.
JSON5 is advantageous because it's explicitly separate - it has a different file extension, it needs different libraries. Also it supports a few other utility features people want (like trailing commas) without bringing in the whole dangerous kitchen sink like YAML does.
That looks like a worst of both world solution IMHO.
You are probably better of with a TOML -> JSON mapping and would be better of with YAML too if YAML hadn't had really stupid ambiguity pitfalls.
- JS syntax compatibility (low cognitive overhead)
- Decent balance between machine-readable and human-readable
- High familiarity for developers (if they know JSON, which they likely do, they can work with JSON5 with near-0 learning curve)