So the custom fields addition is something that we have explored, however, it had to be put on hold for time constraints with other projects. Admin responses have come up frequently and in some cases people have implemented them in clever ways. For instance the user in this thread was submitting response reviews simply by appending “In response to: ” to the front of the review title. Using this consistent format I was able to write some javascript that would resort and apply style to make a more intuitive layout for response reviews. The alternative of creating a response field in the add/edit, allowing for DB space, and adjusting the layout is very much within reach and could be achieved with a few hours of development if you are willing to get your hands dirty. If this is the route you want to go, let me know and I can point you in the right direction.
Cheers,
Charlie Maxwell
[NM_Developer]