I've disagreed with JavaScript before, what makes you think I won't do it again?

Anyway, anything using JSON as a config language will also certainly use a JSON interpreter that can ignore comments. Sure that's "implementation specific," but so is a config file. You wouldn't use "MyApplication.config.json" outside the context of MyApplication loading its own configuration, so there's no need for it to be strictly compliant JSON as long as it plays nicely with most text editors.