My money would be on the EXIF “orientation” property. The orientation property rotates/flips the image (allowing modifying just a few bits instead of having to rewrite all the image data) and support for it is pretty patchy. I would guess that when a Buzzfeed author uploads an image, it gets processed in two different ways: 1. compress the JPEG so that it’s smaller, and 2. convert the JPEG to WebP so that it’s even smaller. I reckon the tool/library used for #1 takes account of the orientation property and the tool/library for #2 ignores it.