Hello Jed,
Thanks for the feedback. Sorry about the quality of the code, will clean it up. Yes, the input is log encoded. I basically took Troy’s Python code that generates the OCIO config, and exposed the params as sliders, so yes, there is a power function at the end (using the ‘gamma’ which is used to place the pivot higher on the y axis). Currently, the pivot is not exposed via sliders, it’s set to mid-grey to be consistent with darktable’s other tone mappers, filmic rgb and sigmoid, but it’s in the plans to make it adjustable.
As for the power vs end of the linear section, I’ve observed the behaviour you describe. It’s really up to users to decide which sliders they’d like to keep - I think it’d be great if we could reduce the number of controls. (Other readers: Jed is the author of the curve, so I think we should really consider his advice.) @s7habo , if you try to re-edit the 1st image of Blender AgX in darktable (proof of concept) - #467 by s7habo with only the toe power, can you make it look the same, or do you find the toe start control is necessary? (Of course, opinions from others are just as welcome, I just remembered this particular image as being an example where the control was used.)
I just discovered yesterday that the humble ‘First time Play Raw poster’ of Rendering Greens is you. 
I’ll start reading your materials during the weekend.