Interesting line of code, there. Do I understand you correctly if I think it allows you to dim the screen to a lower level than the lowest "Simple Backlight" setting?

Here's a couple of related/interesting posts in a related thread.
The first, saying one can write to /sys/devices/platform/omap2_mcspi.1/spi1.2/backlight\:acx565akm/brightness to set any value and it sticks until display is dimmed or turned off.

The other says I successfully disabled my ALS yesterday.

I'm not sure what they're doing there, but they seem to have some success in turning off the sensor.

As discussed in this thread, users coming from the N810 are missing the "Advanced Backlight Applet" that existed on the N810. It had more levels and could go much darker than the default backlight settings.

We'd like to see this ported to the N900. Who would've thunk such a useful applet would not have been ported