When you started your first Discourse community, what did you find hard to do?

There’s a plugin for Discourse called Discourse Encrypt (for Private Messages) that allows people to encrypt their personal messages. So, I imagine, while it may not be possible to create groups or categories where an admin doesn’t have access, I believe people can create group personal messages that are encrypted, thus preventing admins from viewing the group message’s content.

Perhaps that solution would work for you.