Don’t know if I’m to late for feedback, but here we go… 
The tone equalizer is one of the most useful, but at the same time frustrating, modules in darktable.
One of my pet peeves is the extremely limited latitude . +2 EV to -2 EV is far from enough to tame a high DR scene. So almost every time I use it for this purpose I have to stack multiple instances of the module. Even with my extreme take on @s7habo’s linear shadow brightening preset shown below i have to stack two modules.
It seems this could be easily fixed without breaking older edits.
The limited latitude is unlike any module in darktable; most modules make make large shifts with very small adjustments .
The fact that even the slightest adjustment with high curve smoothing values totally flips the curve seems less than optimal too.
I think the mask exposure compensation and mask contrast compensation should be easily accessible from the advanced and simple tabs as it is usually a must adjust these. For me it means there’s a constant flicking between the “advanced” and “masking” tab to make adjustment to make the histogram fit within the boundaries of the “histogram space”.
I almost always use the tone equalizer before the exposure module as I find it extremely frustrating that there has to be adjustments done to my stack of tone equalizer modules every time I adjust the exposure. For my use case the default position would be before the exposure module and the “mask exposure compensation” and “mask contrast compensation” would be automatically adjusted to fit the histogram. I guess the automatic adjustment would be hard to achieve as it hasn’t been done.
Sorry if my pet peeves have already been mentioned in this thread!