[throwaway81523]

You also have to think about security implications of a hostile client being able to crash a remote parser with gigabytes of context, though if it crashes on malformed json then they could do that with a much shorter fragment. In the well intentioned case, being paged in the middle of the night to debug a weird crash isn't fun, so it's better to have an accurate diagnosis (version mismatch) in the log if not prevent the crash outright. There is also the matter of every weird javascript implementation that would have to be updated, if JS can't already accept the trailing commas. It just doesn't seem worth hassling over.