I do know couples that have been divorced for many years and are still living together. It’s “complicated” but none ever tried to sell the house. In all cases, their divorce was finalized and their assets were split. An underwater property wasn’t at issue in their divorces and no one ever tried to sell. Many of these divorces happened PRIOR to the RE bubble and the couple had equity. These are typically “roommate” situations and no one has or intends to remarry. Most of their neighbors are unaware these couples ever divorced.
Often one of the parties was mentally or physically unable to support themselves and so waived spousal support in lieu of free housing. It was a mutual decision, off the books, that the parties worked out.
This is NOT THAT uncommon of an occurrence and NO, Piggs, I am not one of these people ;=)