You bring up some additional good points about voting etiquette. As a general rule, if you make a comment on someone's blog post, it is courteous to upvote the post as well. But if it's a post that already has tons of upvotes and a high monetary value, that might be grounds for an exception (as it is less likely to be noticed). I don't always apply this to someone else's comment, though. If I really don't like the comment, but feel it needs a response, I'm not going to upvote it just because I responded.

As for the minnows making lists of people who upvote their comments, I would say they should probably be focused on producing great content themselves and not be so hung up on what others are doing.