He does seem to be pretty misinformed. For example, he chooses to validate against HTML4 strict, and then compains that attributes like target and width don't v

He does seem to be pretty misinformed. For example, he chooses to validate against HTML4 strict, and then compains that attributes like target and width don't validate. However HTML4 includes two additional doctypes (beside strict): transitional and frameset, exactly to cater to people like him who like to use frame-related features and presentational HTML. His argument about user-generated content is also spurious. If you dont parse and filter user-generated content (with a real HTML-parser, not just regexes), then you are vulnerable to script-injection attack.