Just personally, I think it is in poor taste to leave your own cabin. The reason people do it, if they are honest with themselves, is to have a nosey at people in a higher cabin or to have a bit of a gloat at people who are in lower cabins. IMO, the curtains are there for a reason and they should be impermeable.

Also, just an observation, when people see others going through a curtain - in whichever direction - they assume that they too can go through. On UK domestic flights with BD there is either no traffic coming forward through the curtain or a steady stream of traffic, but never just one passenger on a flight.