Substack can probably give a better answer, but my understanding is that CouchDB only holds a version history since the last replication between clients, and then conflicts need to be resolved before replication can continue, after which version history is lost. With OSM-p2p no data is every deleted, it is all just in the underlying hyperlog. It's more like git than CouchDB, and each record has a complete history, and can be forked and merged and will continue to sync/replicate.