Digital Light & Color

Exactly -- it also keeps any existing command lines in script files in sync with the percentages.

If the metaphor is to be that the LHS of a threshold slider would allow a transformation to proceed at full strength/affect all pixels (no obstacles to it) and the RHS will block as much of the transformation changes as it can, I figured that the following transformations would need a slider direction change:

Blur/Blur More
Gaussian Blur
Precise Gaussian
Bilateral Sharpen/Adjust-Sharpen/Brightness Curve-Advanced mode: BS Blur threshold (sharpen threshold is fine)
Advanced Sharpen: Speck Removal
Sharpen/Sharpen more
Watercolor: Median threshold
Fill Tool
Mask/Flood Fill
Mask/Pinholes? - I'm not sure about it: so far I wasn't successful in getting it to work at all.

Also, a question: is Denoise based on the same algorithm as in PWP7 (which had a threshold)?

Thanks for the list. I think Sharpen/Sharpen More should not be on the list but otherwise it looks OK.

Denoise is unrelated to the similarly named PWP 7 transformation which used part of the raw conversion code.

After making all the changes and playing with it for a while, I think I can say definitively that the result will not make anybody happy. Perhaps I am biased from using the thresholds the way they were for so long, but if anything, I think they should have been the other way around, namely that all the way to the left should have maximum threshold effect and minimum transformation effect and all the way to the right should have minimum threshold effect and maximum transformation effect. I say this because what you see in the preview is the result of the transformation and thus it is intuitive to expect that moving sliders to the right produces more visual effect. It definitely does not feel intuitive the other way.

Sharpen shouldn't be on the list, I realised.

Do you think the ideas of graying part of the threshold slider or introducing some indicators next to the slider's % value display would be impractical too?

I'm no longer sure what's intuitive - I was always trying to think of a threshold as some additional bar that the transformation needs to pass before it is applied to a group of pixels that are above it, but almost always end up having to experiment which way the slider goes (case in point: it has been impossible for me to memorize the direction of two threshold sliders in Bilateral Sharpen even though I use it quite often).

I don't think changing the way the sliders look will make them any more intuitive. Muscle memory based on left or right is effortless -- logical thought based on some indicator is not effortless. There was a great book on web site design published a number of years ago titled "Don't make me think" which I think sums this up pretty well.

I reverted back to the previous code and then reworked all the threshold sliders to work so that moving them to the right maximizes the effect of the transformation. This affected the following sliders:

Adjust (Sharpen Threshold)
Bilateral Sharpen (Sharpen Threshold)
Remove Purple Fringe (Threshold)
Sharpen (Threshold)
Unsharp Mask (Threshold)
Watercolor (Sharpen Threshold)
Mask Pinhole tool (Threshold).

This slider direction appears to me to be the most intuitive, and they should now all be consistent in terms of which direction of slider motion produces the most effect on the result image (or mask).

Perhaps these were implicitly contained in your list: Sharpen threshold in Bilateral sharpen, Threshold in Unsharp mask.

Yes, I did those two.

I just wanted to say, after playing with the new unified thresholds directionality, that I feel it was a wise decision to set them the way they are now (regardless of what the threshold definition may imply in my head). Thanks!