Many thanks for creating this thread @danielle, @RohanM and @oeoeaio 
I think that clear and documented processes are really important in general but especially when there are different teams involved, different TZs and different level of knowledge of the code base and the product itself.
There is generally this idea of core contributors that denotes a group of people that know better the code and the product. It seems that the weight of this knowledge is heavy on AUS team now and we must find a way to spread this knowledge and transfer to other teams.
As per the code review part I think this group of core contributors should dedicate some time to involve other people while following the development of a feature, reviewing the code, etc. Large comments in GitHub doesn’t help much IMHO and some small meeting could help.
One thing that I’ve been seeing helping a lot is splitting big tasks in smaller ones. I know that it seems rethorical but once you learn how to do that you can focus the discussion on a small part of the application without having to explain all the OFN history every time.
This help code review, knowledge transfer, quality assurance (testing), etc… and bit by bit we’ll end up with more people joining the core contributors team.