It was pretty inventive to use English-language as a reason to kill the post (it's not actually part of the guidelines, of course, it's just that almost no non-English posts get upvoted to the front page).

Clearly, it would have been straightforward to replace the link with an automated translation and allow the discussion to continue.

The thing is automatated translations are often awful to read. Hackernews is probably better off waiting for a native speaker to write up something about it because the article will maintain the interest of greater numbers of people

It's not inventive. It has been a rule here since the beginning. I know that because pg told me.

The guidelines don't pretend to be exhaustive.