UPDATE 4:
If the current brightness is higher than 20/255, when inactive, the screen brighntess is set to 20 instead of 1.

I did not test it that much, if you note something strange, let me know.

is this different with rootdim? i always set my screen brightness to 1/255 with rootdim

I had already answered to that.

You can set 1/255 with this mod too, the difference is that you don't need and external app, no background services and you can set 1/255 directly from the statusbar (faster and more confortable in my opinion). Also, there are no brightness increases if you lock the screen with a brightness level < 10/255 and then unlock it (I think it's possible to avoid this with rootdim too if you use "lock brightness" option or something like that).

It's also useful if you lowered the autobrightness levels, because when the phone is inactive or your battery level is lower than 10, there are no brightness increases (if you current brightness is lower than 10/255).