Quote - Yes - hair artifacts.

After studying the material system a bit more on my own, I independently came to understand how to configure it properly.

Basically what we're doing now is to define a hair material and an air material. We use the transmap to decide which points are air and which points are hair. We are no longer thinking in terms of transparent hair or opaque hair. That is the old way of doing things. The new way is to actually make the geometry behave like air wherever we want it to.

I see the artifacts with that shader setup. I also see them with any other setup. In fact, I see them with the hair configured to produce just a solid ambient color without using any shader interaction with light and shadow.

Here is the hair - just the hair - loaded and scaled properly into Kerky. We're looking at the back of the hair.

I'm not sure this is the answer to this issue, but when I mentioned the fact that I had artifacts, one the gurus at the Kerkythea forum suggested the following:
**The artifact on the back is probably because of too low tracing depth. You would need to "apply" the render presetting , then "cancel" and then increase tracing depth in the render window. The other artifact could be because of Brightness Threshold: lower this value to 0.001 or 0.000. After these changes , render again but this time with "custom" settings.
**

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks