The correct place is here: Policy on discussion of the moderation process
Just so that you are aware and expectations are set: there is no specific policy nor oversight procedure for challenging moderation actions. Much of this is being worked out as we speak and is … contentious. Just as anywhere else in life, challenging this sort of thing is especially sensitive.
Frankly, I would not recommend it. Or, at least don’t expect an enthusiastic response nor should you demand an immediate outcome. Say your piece and then let that be enough. These things take time.