I think the salient point of the article was not to use the
disable attribute and instead to use CSS to indicate a disabled state. As I understood the article, they were not against disabling the click per se, but against using the disabled attribute because of its effect on screen readers.
GP by contrast was suggesting allowing someone to press submit multiple times. These are not the same discussion as I see it. My response was more to address that, and was agnostic about whether the attribute or CSS disables the button.
As for using the disabled attribute, I agree with comments that it's not semantic to simulate `disabled` with CSS when we have a perfectly good disabled attribute, and it's the responsibility in this case of the screen readers to render this situation as it is meant to be understood. I'm open to reasonable disagreement here but I think the consensus is that the article is incorrect.
As for allowing multiple submissions, I think it's probably a good idea in general to program defensively against duplicate submissions and return a 409 when in doubt. But the user experience is improved by not allowing duplicate submissions on the front end for several reasons, among them that it's confusing. A POST is not idempotent, but allowing multiple submissions treats it that way.