It seems like everyone agrees that the term hardcore is mostly undefined, right? Well, then this article is useless, since anyone can set their own personal parameters to the term itself this only means that subjectively in the authors mind, this is how things are but not objectively.
If you ask a hundred people what "bright" means (as in lights) you'll get quite a few different answers despite certain people agreeing and no one is wrong (and, subsequently, no one is right either).
The article itself is fine but it implies that the author has the final authority on what hardcore is or isn't and that's a tad pretentious to me.