In responding to comments, if you even do this at all, a simple "thank you" is sufficient in response. Especially if the commenter has taken the time to leave thoughtful feedback.

Leaving wise-ass remarks, or failure to say thank you at all after responding to a question or thought that might have been included in the comment, is extremely rude.

People on this site have no manners anymore. x(

(No, this is not referring to anything specifically--it's just a common trend I've noticed recently that I find incredibly disheartening.)