ANyone that leaves a thoughtful comment on one of my posts, I will give an upvote to. Anyone that leaves thought provoking comments on other peoples post I will usually also upvote. I don't really have a set number in mind but I think it is something similar to your, 10 - 30 per day. I agree, curation and discussion are fundamental to growing the user base on this platform and upvoting comments are one way to do this