Result: 2♥(E)=, NS -110.
I was called at the end of play by North, who was not happy with West's sign-off in 2♥. I looked at West's cards and couldn't see what the problem was, but North wanted to know why he hadn't made a game try. I asked West, and he said that he has invitational values but that the hand looked like a misfit, and partner can always bid again with a strong hand.
I said I'd get back to them and wondered off to study the hand record. Now I found the problem. North thought that after a fourth-hand opener, West shouldn't be so quick to give up on game. I went back to EW and asked East why she had opened this hand, and looked at what their convention card said about one-of-a-suit openers.
There was nothing on the convention card to indicate light openers in any position, they were playing a fairly standard form of Acol. East explained that in the protective position they "transfer a king" and open lighter than usual. Both East and West were surprised to be asked, and thought that what they were doing was completely normal.
What, if anything, should the director do?