For me personally, there's nobody I automatically upvote. There are a few people who get the benefit of the "PG effect" in that I automatically associate their name with specific domain expertise and give them the benefit of the doubt within that domain.

What I have found is that writing comments that get upvotes provides valuable feedback about the mechanics of writing comments that get upvotes - just as writing downvoted comments provides feedback (more quickly). Writing one good comment increases the likelihood of writing another one - writing bad comments, also increases the likelihood of good comments via downvotes.

HN provides editorial feedback in a form other than LOL's - comments and votes. Editorial feedback is a proven way to improve writing, and improving writing is the surefire way to get higher comment scores.