That graph makes it look like Rainbooru is less restrictive than the other boorus. Technically I think it's the case. But in actually, the way you guys described the moderation and community attitudes there, they're deceptively the opposite.
We have a DNP system….
Manebooru looks to be Rainbooru, with DNP.
Twibooru seems to be the only one that appears to be the more free rolling unrestricted image host.
If only we could strike an alliance of some sort with some of the more like minded boorus. I can totally see some of them being true archives.