http://test2.wikipedia.org/wiki/File:Portrait-rotated.jpg
The image at that page should be 600x800 px. However, its resized to 450x600 px which is the right aspect ratio but too small. It's then upscaled by attributes on the <img> tag, which makes it look crapy.
I have no idea why this is happening. It works fine on my local checkout of REL1_18 and my checkout of 1.18wmf1
Version: 1.18.x
Severity: normal
URL: http://test2.wikipedia.org/wiki/File:Portrait-rotated.jpg