Maybe "married" needs clarification in this discussion. Or perhaps I'm the one who needs clarification. There are married people who live apart and are essentially divorced, but are still married for convenience or property, etc. And there are PLENTY of people who cohabit, as if married, but are not married.
Surely you don't mean that it would be OK to have a fling with someone who was unmarried but cohabiting as if married? And likewise, why a strict prohibition on someone who's well-separated but still legally married? Is anyone here attaching a moral significance to the legal state of being married?
Or are we using the word "married" to include people who cohabit?
I'm asking because it seems the preoccupation with marital status alone is somewhat inconsiderate.