Stable OOS 5.1.7 and GB 8.4.1 for Oreo, running through old Xposed... Haven't updated either one in many months.
I thought in the past that Quiet Hours mode blocked notifications from showing on my lock screen at night.
Recently, I noticed the room lighting up when notifications come through.
Confirmed Active Screen is turned off in GB.
I have no lock screen (at present).
Has it always worked this way, or did I mis-set something?
Only about suppressing properties like LED/sound/vibration. This means behavior you described is OK according to current design.