I agree that responding to your audience is important. I also always try to respond. Only in cases someone says "great post!" or equivalent, I might not respond. Most of time I still thank them, unless I think they are just spamming in the hopes of an upvote.

On the up vote thing, I'd also like to give more upvotes to people who comment on my posts, but since I loose 2% voting power from a vote, which is worth $0.01, I think no one really wins if I upvote. When I have enough steempower to start giving % amounts, then I'll most probably start giving upvotes more often. Now I just do it on days when I don't really find much content to upvote otherwise. So as to thank the people with a gesture, more than a financial reward.