More generally, I don't think that social approval/stigma are bad things. They are the glue that binds civil society together. I can't help notice that people when people speak negatively of social pressure, they never apply that critique generally. Should there be less social stigma against racism? Less social stigma against harassment? Suddenly, they're not so sure.

I'm a lot happier with social stigma when it attaches to acts and fades in proportion to time distance from the act, at some rate inversely proportional to severity, rather than attaching to immutable properties (whether or not they derive from some act). If I hypothetically get plastered and vomit strawberry Jello shots and half-digested guacamole all over my friend's expensive Persian rug, chances are my friends are going to give me a lot of shit about it, and to be a little more cautious about inviting me to parties for a while... but I do not thereby become Gest the Puker, then and forevermore. Divorce has traditionally not had this property.

I might make an exception for crimes on the level of murder or rape, on the grounds that those are so severe that the stigma shouldn't vanish in a normal lifetime. (Though on reflection, I doubt I'd think much less of him if my grandfather revealed that he'd killed a man in his youth.) But if we're going to be treating marriage as a civil contract like any other, then breaking it is a civil matter, not something on that level.

If doing X would upset (or please) your neighbours, your choice (not) to do X is still voluntary. It just means you're facing a trade-off. Welcome to adulthood.

For some value of “voluntary”, sure. Likewise, for some value of “voluntary” if I point a gun at you and ask you to do something, your choice whether to do what I ask or be shot is voluntary.