This answer has 3 images on the i.stack.imgur.com
domain that are appearing like this:
This related question: My Stack Overflow imgur images are disappearing has an answer by Pekka 웃, suggesting to change the URL from i.imgur.com
to i.stack.imgur.com
.
Here though, the opposite is true - changing from http://i.stack.imgur.com/hAPTu.png to http://i.imgur.com/hAPTu.png finds the image.
Maybe it's worth pinging Alan?