I would be surprised if the only criteria for feedback were to be feeling, however to leave that out would be to leave out the most essential information in regard to response to a client/work. The point is that feelings are not intellectual or academic, they are a true response of ourselves. They offer invaluable information as to what is going on in another, and also about our own personal response and feeling. Without a sense of awareness or feeling, Gestalt cannot be practised effectively.
There is no Gestalt criteria for giving feedback as such, however opinions can mask feeling responses, and Gestalt has a strong emphasis on feeling and awareness here and now. This needs to be integrated with intellect, not divorced from it. Sometimes one or other of these areas are less developed and then we need to practise the other, and find ways of integrating. I hope this makes sense.