There has to be some form of voltage drop across the bulb, implying current flow, for this to happen. I am going back to the theory that the switch is switching the neutral instead of the hot lead. That is a potential safety issue, so I would check that out.
Initially real estate electrician checked the fixture while the switch was turned off,,,,and there was current (checked by Electrical test pen),,,, he thought initially problem with the switch is not working properly.
He checked the switch, that has two wires one has current (checked by Electrical test pen) other wire doesn't, unless you switch it on
My guess I might be wrong that test to the switch indicated there was no problem with the switch, but why the wire that is connected to the fixture still has current while switch is off!!!!!
My guess I might be wrong and that test indicated that the switch is not switching the neutral instead of the hot lead, because when the switch was tested by Electrical test pen one wire has current and other wire doesn't, unless you switch it on.
Any way he replaced the switch with new one still same issue......
He checked other room it had same thing....
I was renting different house before this one, both houses are in the same area, in my previous house I had only one room was doing the same thing but I didn't bother to call real estate to check that for me.
Then when I moved to my current place also one room is doing that