has there been any standardization efforts which didn't end up with implementation-specific changes everywhere? admittedly the worst example for such a topic,

has there been any standardization efforts which didn't end up with implementation-specific changes everywhere? admittedly the worst example for such a topic, but, we still don't have a situation where all browsers agree on all renderings, and all of them still don't follow the spec, and in some areas, they don't plan to. I can see html requirement being a pain-point for anyone implementing standard markdown.