This idea was taken by me from htc amaze 4g thread for disabling capacitive button backlight.
I have modified it for mtk 6577 based phones to disable button backlight.
Just open terminal and paste this
After entering su
mount -o rw,remount /dev/block/mmcblk0p29 /system
chmod 777 /sys/devices/platform/leds-mt65xx/leds/button-backlight/brightness
echo 0 > /sys/devices/platform/leds-mt65xx/leds/button-backlight/brightness
chmod 444 /sys/devices/platform/leds-mt65xx/leds/button-backlight/brightness
mount -o ro,remount /dev/block/mmcblk0p29 /system
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