[MLonlooker]

I don't know the answer but I would speculate the the highlight outlining that we are discussing the reviews is somehow related.
This outing may be very distinct with highlights due to their brightness. However, at less contrasty edges the same outlining may produce the shadows.
However, don't ask me what's causing the outlining in the first place.

Thank Klaus.

I was surprised by the bokeh in the jalopy image, other images looked fine ....

All the teles I have shot with have an issue with highlights as well as nisen bokeh, which makes getting a good image a struggle ....

Both these images were taken at ground level and the effect is alleviated:

https://www.flickr.com/photos/[email protected]/

here the transition around the plane of focus remained edgy/gritty and PP was needed:

https://www.flickr.com/photos/[email protected]/

Both taken with the AF-S 600mm F4E FL wide open .....