Currently when a new review is added it appears and there is no way to alter this behaviour.
According to: https://wiki.ubuntu.com/SoftwareCenter/RatingsAndReviews#Moderating%20reviews there should be two modes active and passive.
Although this could be implemented via a setting, we really need this to be configurable in the admin (rather than by updating a configuration branch), so it might be worth briefly seeing what others do for key/value setting-type info in the admin (although a simple model would work - AppOption just with key/value attributes).
QA Notes:
0) In the admin, ensure that there is no RNRSettings record,
1) Create a review via the client,
2) Access the /admin/ and verify that the review has False for it's 'hide' attribute (ie. it is unchecked)
3) Create an RNRSettings record in the admin, and set the moderation mode to Active.
4) Create another review (for a different app),
5) Verify in the admin that the new review has True for it's 'hide' attribute
6) Update the settings record, setting the moderation mode to Passive
7) Create another review (for a different app),
8) Verify in the admin that the new review has False for it's 'hide' attribute.
Note: the USC client will always show you the new reviews you add, whether or not they are hidden to everyone else.
For some reason the value for activer mode & passive mode was being saved as a string u'1' instead of as an integer even though the field type was SmallIntegerField. I've fixed this now.