The name is definitely confusing though. You're creating a new format that existing JSON parsers cannot handle. In a way, it's like creating a new XML format called XML2 that uses parenthesis instead of angle brackets, and standard parsers like libxml will no longer be able to read.
Future newbie developers will wonder why their xml reader has problems reading document.xml2 without actually realizing the format is different from xml.
It's worse in your case since JSON5 almost looks like regular JSON, but if one were to use one of your special features, it would cause any normal JSON parser to break. The newbie developer might not be sharp enough to realize he needs a completely different parser.
Future newbie developers will wonder why their xml reader has problems reading document.xml2 without actually realizing the format is different from xml.
It's worse in your case since JSON5 almost looks like regular JSON, but if one were to use one of your special features, it would cause any normal JSON parser to break. The newbie developer might not be sharp enough to realize he needs a completely different parser.