GoKawiilNeovim overwrote and deleted legacy Vim persistent undo files
Computer scientist David Chisnall reported that installing Neovim caused it to detect existing Vim persistent-undo files, delete their contents, and replace them with a new incompatible format, without renaming or upgrading the originals. He said Vim itself could no longer read the resulting files either. When he raised an issue about the data loss, he was told the persistent undo file format is considered unstable and not guaranteed to preserve data.