Love! LOVE, love love. (Did I say love enough?). This was exactly what I needed, which was a way for moderators to moderate users (what a concept!) without having to give them access to the ACP.
I ran into one snag, because I am still learning about xF's details. This add-on checks the secondary box for whatever usergroup you designate as moderated. But because primary permissions override anything in the secondary group, nothing was happening to those users. The secret is to change all "no" in the group's permissions to "never."
I asked Andrew about it and he immediately responded with an answer. Thanks, dude! You and this add on just rock.