Description
AEM has a user synchronisation capability in the publish tier. The synchronisation mechanism relies on FileVault to export and import content.
Users stored in the repository under a path that starts with a _ and that contain another _ can be exported but fail to be re-imported. For instance, the user stored under the path /home/users/test/_6k_test-user-a won't be imported.
Debugging this issue, it seems that FileVault treats the 6k pattern as a namespace and thus skip the resource upon import because the paths don't match.