Maybe there is something to what that poster said about the MO world being different as per socializing as a couple.
But as concerns the “Yeshivish” crowd:
I heard from some reliable and mature friends in Maalot Dafnah and Arzei HaBirah that sometimes these innocuous looking “couples’ meals” have led to serious problems -some of which have had irreversible consequences.
It’s not just another chumrah -it’s just common sense.
The immature young and beautiful open-minded types are still welcome to insist that it is all innocent fun and games, and that any social contact with the member of the opposite sex is suddenly muttar after you’re married. Besides, the men aren’t socializing with the women… Or are they? True, most of the time people stay within the confines of decency -but you never know whose marriage is already 3/4 on the rocks and suddenly finds understanding by a friend who is -whoops!- a member of the opposite gender…
It may start in the presence of the involved parties’ spouses, and it may end with recriminations shared by the guests/hosts after they get back home. But sometimes -as rare as that may be -it doesn’t. And that’s more than a good enough reason not to socialize as a couple.
One who doubts this should consult Rabbi Yitzchak Berkowitz or Rabbi Nochum Eisenstein and ask them what their opinion is on such meals.