I think negative feedback on a suficiently old story (depending on what sufficiently means) is sorta like criticizing the Egyptian Pyramids for not being the Pyramide du Louvre. Doesn't make much sense, and there's not much that one can answer. Maybe a "Thanks for your input, I'd love to know your opinion on <*insert newer work here*>".

IMO, feedback, constructive feedback is always good. Positive, any kind of positive feedback is good in a people care sense.

As how to responde to negative feedback, *shrug* the written medium, especially one as the Internet, is not conductive to having your opinions perceived in the correct way. I know I've had people misinterpret me. I'm sure I've misinterpreted people. You can try not to sound defensive, but without body language to help interpret your meaning, people might take it the wrong way, so, unless you know the person it's a roll of the dice.