We have a hair salon and customers sometimes provide positive and negative feedback via a survey. Some of these are anonymous and we are unsure who it is and some are not.
At the moment we have been simply printing off the negative feedback and giving it to the person without entering into any discussion (they often want to justify why the customer was unhappy) so we simply pass it onto them saying we thought you would like to know. With positive feedback will pass on direct feedback, post on the salon page and also on the team facebook page.
When an unhappy guest provides negative feedback and we are not sure who it was specifically what should/can we do (I always contact the guest to ask for their details and try and resolve their issues).