Feif: When you talk about separate seating, are you talking about in your house, or at a large communal meal like a wedding or dinner.
The story of the chofetz chaim seems to be a meal in his house. What information do you have about what they did in Europe for large communal meals?
I also don’t really see how anyone could have a problem with it. To state: “there is absolutely no reason for it”, would be utter foolishness.
To say that it causes very much hardship or discomfort is also foolishness.
So maybe they didn’t do it 50 years ago. They also had mixed dancing at shul dinners 50 years ago. Big deal.
Besides, why is the relevant time 50 years ago? Why don’t you ask whether they had mixed seating in the time of the gemara? Like the gemara which says that men who teach young children are suspect because the mothers come and pick them up from school.