Saten and I had an interesting conversation about this.Just make it so we can use osu! in-game chat like it was IRC. Let us create channels and moderate them. Some groups of users who have enough knowledge to do so already do this on IRC and don't even use osu! chat. If a channel is 100% private it shouldn't need any kind of moderation. Of course, peppy should have administrator privileges and access to every channel just in case. But really if I make a chat channel with 10 friends and we want to talk about porn then why do you mind, we already do this for talking "forbidden matters" on #spectator or other chat platforms.
There must be an limit of some sort. Or else this would start to require moderating if things happen. I think one of the reason why people don't like to use the multiplayer chat is because there's only 8 slots. but can't someone just leave in case they're not having the conversation anymore? Not even #osu has conversations with over 8 people at the same time.
but don't get me wrong. This would be amazing for me with my closest friends since we're all connected in a way and we'd all love to discuss with each other in private, together sometimes.
Public channels would require moderation yeah, but then again you can just don't allow those and allow private ones. Just as you get auto-join to #osu and #announce when you log in, getting auto-join to some channels I'm subscribed/invited to would be cool. Then you need no real moderation. Just give privileges like kick/ban/invite to channel moderators, same to room creator + change password/disband channel. This won't really hurt anyone and it would make people use osu! chat more than they do now, since actually there is no way to have a nice chat group without having to go into #multiplayer (meaning you can't just go, play and read later) or #spectator (same, and this is a public channel).
Only thing that's bad about this is we're gonna be able to... chat group about almost whatever we want on osu!, which won't really hurt anyone. There may be more consequences but I can't think of any bad one, like having public channels lose some people, which isn't really bad at all for... anyone.