> "query strings are horrible"

That's not at all what the article says. You're responding to a weird strawman that doesn't resemble the article's actual point.

> foobar.com/ducks?pdf

This isn't relevant when talking about links to his site. This is relevant when talking about links to your site.

> Besides, what does it mean to "ban" it? You simply don't respond to query strings you don't want to handle.

It means that you're going to get some sort of 400 error when you follow a link to his site with a query string attached to it. He simply will not respond to query strings that he doesn't want to handle, which is all of them.