So you may have noticed that your display brightness adjustments seem to have little to no impact or that brightness changes randomly. This is because the default Windows configuration on this system has adaptive brightness enabled and (when on battery power only) the Intel GPU drivers have Intel Display Power Saving Technology enabled, both of which can cause these issues. The former uses a built-in light sensor to adjust display brightness, much like smartphones do, and the latter can alter the behavior of the LCD backlight. However, it seems people in general appreciate this type of behavior far less on their laptops than on their smartphones.
How to disable[]
For adaptive brightness, go to Control Panel > Power Options > Change plan settings > Change advanced options > Display > Adaptive Brightness. Disable it for battery and/or AC power, and for any power profiles you may use.
For Intel Display Power Saving Technology, go to Control Panel > Intel HD Graphics > Power > On Battery. Disable "Display Power Saving Technology". This does NOT need to be adjusted for each power profile in Windows.