I am currently running Raspbian Stretch and I'm using the official 7" touch display.
By default, raspbian would turn off the display (including backlights) after some timeout (30 min I believe). At some point, I installed xscreensaver to see what my options were, but eventually decided I preferred to have the screen actually turn off rather than use a screen saver. The problem is, the best I can get now that I have installed xscreensaver is to have a black screen with the backlight LEDs still on. I have tried using xcreensaver "Blank Screen Only", I have also tried "Blank Screen Only" in conjunction with Power Management and "Quick Power-Off in Blank Only Mode." But I still get black screen with backlight LEDs at full brightness.
How do I restore the original functionality of turning off the display, including backlight LEDs?
edit: I should add that I have also tried uninstalling xscreensaver, which did not revert the system back to default settings.
edit 2: I updated my firmware to 4.14.27 from 4.9.59 with no change in automatic behavior. I also have verified the existence of /sys/class/backlight/rpi_backlight/bl_power, brightness, etc. I can also successfully update the values within these files, but they seem to have NO EFFECT at all on my screen brightness or backlight. I am also using a screen with a V1.1 controller board.