It is better to have standards that everyone can quickly conform and adhere to, rather than standards that cause everyone to be '99%' compliant, because that '1%' tends to grow into a large collection of 'forbidden' features once you consider multiple implementations of that language, and the fact that each of their '1%' is not the same.
Having a standard that says you are ABSOLUTELT NOT ANSI compliant unless you are 100% ANSI compliant would be a good start. After all, every compiler maker likes to advertise '95%' (or whatever) ANSI compliance, sometimes for years, rather than sit down and become 100% compliant (or as near to that as is possible).
