I have published a utility that will let you see which areas of a Sony raw image are using high tonal compression. The utility generates a color-coded PNG depicting the compression - you can then overlay this PNG over your raw file in Photoshop to correlate any perceived artifacts to the compression. I created the utility to address the myriad of IQ complaints/artifacts people are attributing to the compression online ("orange peeling", jagged edges, posterization, etc..). So far the only side effect I've been able to correlate to the compression is shadow artifacting on high contrast edges (here), and this is after comparing about 20 identically-shot images between an A7r and D800.
You can read about how Sony's raw compression works here, and instructions on downloading+using my utility here.
Here is a sample A7r image and the compression PNG overlay generated for it: