Yeah, I was wondering that, too. UX can cause harm, for example, certain kinds of contrast and lights for folks with epilepsy, but I'm not sure that the complaint here rises to that level.

If you can't use something, you could argue that it causes "harm" to your well being or job prospects or something.

But I agree that "harmful" should probably stick to more significant, mostly physical effects.

But, of course, here we are on HN discussing it, so it had its desired effect...