First people said it didn't exist. Now people say it does exist, but only if you push six stops. What's next: people saying they actually like how it looks?
DpReviews didn't write this article because they think the compression doesn't matter. Their examples aren't all processed with a six stop push, either. As they note, the compression will change some peoples' exposure routine by more or less ruling out "ISO invariant" metering. Which will in turn affect the available dynamic range.
For some subjects, the artifacts are pretty strong, requiring cloning or other invasive post-processing.
By the way, this is not the first visual example of the compression, by any means. The issue has been demonstrated several times. I found artifacts in a downloaded A7RII RAW file that I processed using a moderate shadow boost, similar to processing I often do. 100% crop:
Other people have provided other examples.
This compression wouldn't prevent me from buying an A7RII. It's a secondary issue. But I'm glad to know about it, and would definitely take steps to manage it in situations I often encounter.
--d