Via the AdminCP you can disable or enable turning rep off for each usergroup you have.

Sounds like it is enabled for the moderator usergroup but disabled for general membership usergroups.

If an admin wants to enable the turn off rep function, just go to edit usergroup (for each usergroup you want it enabled) and it can be done there.

Looks like for the registered usergroup I can give myself rep but nobody else.

That might want to be looked at too. I can't remember if that is through the admincp>Vbulletin options> reputation options, or edit usergroups like above.