My point is that if you're in sufficient control of the stack to be able to convert the whole thing over to YAML, you could just as easily convert the whole thing over to JSON+Comments. And of course bad things would happen if you treat JSON+Comments as JSON, but similar bad things would happen if you treat YAML as JSON, so I don't see your point. It's not like people are trying to send their tsconfig's on the wire as "application/json" and expecting arbitrary parsers to support it.
Then it's not valid JSON, and if you try to treat it as such bad things will happen.