What do you mean by "civilized jurisdictions"? I don't know any place that explicitly adjudicates the separation of unmarried couples as though it was legally e

What do you mean by "civilized jurisdictions"? I don't know any place that explicitly adjudicates the separation of unmarried couples as though it was legally equivalent to a formal divorce. You'll have to be more specific. Unmarried couples may fall into one of two types: common-law marriages and meretricious relationships. In the US, the former is approved by a vanishingly small number of states. The latter has no legal rights to property division or palimony without an explicit cohabitation contract. Even then, many states don't recognize palimony at all.