Keeping a private forum for moderators discussions is standard practice in the forum world. You do not want moderators discussing issues in the forums, including things like how to deal with reports or problem users, in a public place. And it is also standard practice in the forum world to keep conflicts among those teams backstage as much as possible. The reason, I think, is clear from current events. Many forums would ban mods/admins who take backstage conflicts out front. We don't, but that doesn't mean we shouldn't try to settle them backstage before they become public.