(left: original, middle: this paper with τ = 0.5, right: imagemagick contrast +15)
Notice that the bow-shaped part enclosed by her hair at the bottom of the photo becomes much brighter than the body after contrast enhancement. This closed area becomes a separate hillock during sweeping and is stretched more than other parts due to a looser constraint (6). This becomes pretty noticeable with increasing τ. With that said this paper does a pretty good job at enhancing the texture of the hair.
I suppose this approach should work well on images with high contrast as it avoids over-saturating pixels, but then I have no idea how well it compares to other tools available in darktable/RawTherapee.
Yeah also the nose is enhanced quite strongly. But let’s put it this way, I could live with some larger, easy to separate areas where some “artifacts” are created if I get some nice local contrast in the complicated parts like the hair, the feather and the hat. Repairing these “artifacts” is not that hard.