These pictures match what the site is supposed to be doing perfectly.
Here's how it works (and how it should continue to work):
If your picture size < 125K, it is left unchanged.
If your picture size > 125K and the width < 600, the image is recompressed without changing the dimensions.
If your picture size > 125K and the width > 600, the image is recompressed with a width of 600.
Please don't change this algorithm. Pictures look lousy at 600 pixels wide, so I always take care to transcode my images to be under the size limit.
hmmm, then how come it didn't recompress the photo above?