User blog comment:FlammeumDraco333/1.5.2 Multiplayer/@comment-25373667-20150403144342/@comment-12161342-20150403150719

If someone gets 1.5.2 to battle you, they have to completely uninstall vanilla 1.6.1. THEN, they will not even be able to play with Hansa or SWC if I remember correctly.