You’re completely right. Nobody knows what’s going on behind closed doors, nor what goes on in another person’s head. The whole world may think one way and so sometime even would the spouse in the second marriage with whom the affair took place.
But some may feel guilty but never admit it, show that they’re happy and not directly express their regret of inflicting trauma on their children and even first wife /husband from their their previous marriage. However, for all intents and purposes, they look happy and so are assumed to be happy. Longevity in a relationship doesn’t always indicate happiness. Those who have absolutely no feelings of regret or guilt for their deceitful lies, well then that would show what kind of person they really are. Those with a conscience, might be happy in their subsequent marriage after the affair, but would at least feel guilty/regret hurting others. Also, to have compassion for the people who have been hurt and are reminded daily of said affair, no matter how they show that they’ve forgiven and have moved past it, should not be that difficult.
I agree with the PP who said that marriages after affairs started as a fling may not last when there was never love there as opposed to those that started from a place of love. Of course, if a person who has been cheated on, nobody is going to spout the statistics when marriages after affairs do last. There’s nothing wrong with trying to console someone whose world has fallen apart so to gloat and say that actually I know of marriages and relationships borne out of affairs to last is actually seems quite spiteful. But if one was to prepare their friend and loved one and say that this may be a long-term thing and you and the children may need counselling to handle this trauma and that you’re there for them would be fine but not immediately once they’ve found out about the affair. That’s precisely why posters on MN can’t say that as they don’t really know poster IRL and so can only provide support, console and provide platitudes and give practical advice and that’s ok too.
As for C&C, I can’t really say. She does children and grandchildren from her previous marriage so it would make sense if she wants to keep a space that would be comfortable and convenient without any thoughts of royal protocol. I can’t say I blame Camilla for that. It seems very practical. Besides, they can afford it so why not?