"I don't think this comparison has any place in this discussion"

I agree. Comparing markup languages to programming languages is even worse than comparing js to assembly. But since we are on the topic... I am not quite sure i undestand what " xhtml is unsuitable for the real world" means. Xhtml is a contract between a content author and a browser. Why do we call the browser's failure to implement the contract "unsuitable for the real world"?