...from a question on Dpreview regarding the extremely light tones in the child's face.

The 'black dot' on the curve was sampled from the woman's face and the 'white dot' from the child's.
The white dot is at a value of 242+ and is roughly a 'paper white whereas on the woman the sample is a value of 229.

What this means in practice is that in an 8 bit Jpeg there is not enough information to darken and separate the tones properly in the child's face.
However I bet that it is easily there in the RAW file unless this has been previously manipulated.

This is actually a reasonably good example of why many of us shoot RAW or RAW+Jpeg.

When we start to approach a value of 255, one or more of the RGB channels are likely to clip and (pretty much) all is lost.
And in extreme highlights, when in 8 bit Jpeg...any attempt to darken and separate tones will likely posterize.