I haven't looked deeply at the code, but it seems that when you view the image it is cropped to the width of the content-wrapper div. In many cases the image (when you view it) is wider than that. I work around it by right clicking on the image and selecting 'open image in new tab' but I was suggesting it would be nice to left click on the image and have it open in original size (or something like that).
What I took the problem to be was viewing the image, rather than editing posts.