Well, I experienced some hassle on the domestic sector, so considering I was just in transit on a SYD-SGN-HAN-LHR I certainly was on a domestic segment connecting from and to an international flight.
Well at the domestic lounge in SGN they tried scanning my boarding pass which apparently didn't do anything, then carefully studied my Alitalia card, asked me if I was connecting to or from an international flight, I said yes, and then they said "oh sorry sir, you can't access the lounge".
Eventually after a bit of discussion with them, they called their supervisor and I was allowed access. But they really didn't know the rules and just said something that seemed convincing until I debated otherwise, they were friendly and polite though.