Whatever the solution, Wray is spot on that customers need the keys to end communication with the developer at any time.
That being said, I think Wray’s distinction between public and private seems unwieldy. Reviews are public, so it makes sense that replies to reviews are as well. By forcing publicness, the procedure is simplified (encouraging users to actually enable feedback) and helps to keep the members of the conversation in check.
I think it should be implemented as follows:
There is a checkbox when leaving a review for the customer to allow responses from developers; the default should be to leave the option unchecked.
Responses appear on the app’s page beneath the original review. The customer is alerted to responses by some UI in the iTunes Store and, maybe, a push notification on their iOS devices.
At any time, the original reviewer can close the discussion ‘thread’ to any more responses. This decision should be displayed in the review section to clarify that it was the customer’s choice to end the conversation, rather than the developer’s lack of care to reply.
If the original rating or review is changed, the associated thread is deleted. This ensures that future readers are not confused by mismatching incongruent comments, as well as preventing App Store pages to clutter with outdated information.