The user accounts module that was previously has hard-coded to check for user permissions. You weren't really able to use it without admin/superuser permissions. This was by design, because of the potential social engineering and other security concerns. The persona bar is not much different.
If you want to assign user management tasks to non-admins, you'll want to be very careful on assigning those duties, and you'll need to use a third-party or custom module to do that. Here are a couple of third-party options I found.
- UManage by OPSI srl
- User Management by Upendo Ventures (revived from an archived version originally by DNN-Connect)