Every node edit goes through nodes_history: title, markdown body, sort_key, parent are all snapshotted on each change. The data is preserved; what's missing is one-click revert tooling.
For now, recovery is manual: open the history, find the prior version, copy the text back into a patch_node or update_node call. Crude but reliable, and the audit trail itself stays useful for understanding why a section is the way it is.