stillalex, i would be really surprised if removing a 'mandatory' would have any impact. while i don't know all the details of the nt-code-base in oak, i can assure you that i am not aware of any regression/ticket/complain associated with dropping the 'mandatory' from the "rep:password" property quite some years ago. so +1 for the proposed fix. if you don't mind, i will also link it to the corresponding issue that made us aware of the problem.
anchela, mduerig any ideas of what the impact on changing the node type definition might be? hopefully none?