Here’s an odd one. Apparently at random, an image will fail to show up for some users even though it’s visible to everyone else.
For example, the following post displays a “broken link” icon inside the space reserved for the image for me, but others see the image displayed correctly:
FWIW I’m running Firefox 42.0 (Mac). I have NoScript installed, but all scripts are allowed for the forums. Here’s what I see: