1. Log in as superuser on author
2. Change the password for a superuser
3. Activate the superuser user (to propagate changes to public instance)
--> You get an JS alert error "Can't Activate...."

I guess because Magnolia uses current user to log in to the subscribers, when you change your password authentication on remote subscribers fails....
If that is the case, then there has to be a way to propagate the new password before the authentication occurs or use the old password, authenticate and then update subscribers...