I’ve certainly wanted to be able to do this for Bingo Machine in the iTunes App Store. I don’t think Apple has done this as of yet, as they foresee the functionality being abused by some developers who post snap-retorts to 1-star reviews.
Even Google is wary in rolling this feature out; a response cannot turn into a threaded conversation and the permission has only been given to a small curated set of developers, for now. A developer can only respond once, per comment. I think this great, and stunts most trolling opportunities upfront. If a customer wants to talk more, they are encouraged to take the discussion to a private channel, like email.
I think these restrictions are very sensible. This could be a really helpful addition to the store.