I use the tagging feature frequently in KDE to organize a list of markdown files. when I tag a file with dolphin then open it with kate, and save it again, the tag will be lost ... I think this should not be the behaviour.
Known issue: This is due to using to a temporary file first, and in case of success we move the file. This avoids data loss in case of crashes etc, but of course leads to this bug. Tracked in bug #333577. *** This bug has been marked as a duplicate of bug 333577 ***