I think both public and private channels for complaints can work.
We had a public forum because people coming from the game server usually didn't know who to complain to. Once they had posted their complaint, usually the relevant admin would respond. Then they could settle the case in public or in private as they wished. I supervised to ensure everything went smoothly.
The complaints forum permissions are set so that you can post a new thread and respond to posts in that threadm but you can NOT post in a thread that you have not started. Admins can post everywhere. So you can't sign on and start posting in support of your friend. Maybe this is why there was no flame wars ever started, even in that explosive evironment. 95% of the threads went this way:
Player: I was banned last night. Why?
Admin: You shot a team-mate and stole his plane. That's against
our rules.
Player: Oh, sorry. I hadn't read the rules. Won't do it again.
Admin: Ban lifted. Enjoy the server.
Another reason for doing this in public was to educate people. They would see this exchange and understand how we ran the servers.
I really don't expect we need all this for the Uru crowd, but it's better to be prepared, and it is always better when things are clear.