I am still Ok with -22, but I have 1 new comment raised by introduction 


of the base64 ABNF non terminal:






I think it would be worth adding a comment for b64token that points to 


the base64 RFC. The current ABNF is too permissive (arbitrary number of 


"=" allowed at the end) and there are enough broken base64 parsers 


around (parsers that ignore everything after a "=", parsers that support 


arbitrary number of "=" at the end, etc.), so we shouldn't encourage 


creation of new ones.