how could you miss this with initial cross browser testing? If I were the company i'd be furious.
On another note. The payment processor we use (2checkout) have an error in their checkout page where they ask PIN code but explicitly point out _Only required for US customers_ but in reality it is needed for ALL customers. Raised this bug two months ago, they acknowledged it and it is still not fixed. I'm furious at this but based outside US I have little or no option to switch.
Agreed. However...
"Probably their QA got fired after this event."
I doubt it. I have seen many QA staff at a variety of companies get so used to IE's various oddities that over time they will simply stop opening some kinds of bugs against the site on IE, even perfectly legitimate bugs like that in the article. All it takes is for product management to punt mixed content warning bugs during a few releases before QA also stops reporting them. If someone does later bring one up, over time it evolves into "Oh, that's an IE thing we can't fix." These are smart people doing generally diligent work, but they do tend to get worn down around IE.
I can't say for sure why this happens but I've seen it most with IE mixed content warnings.