Not related to this article, but this post seems to attract so many cranks. Just look at other comments. The amount of weird (out-of-touch) comments on this post is fascinating.
You do get some minimal upgrades with enough karma, like the ability to downvote. But it's not like you get any priority or special treatment, and the numbers are not exposed unless you open individual profiles.
I suppose it could be useful to give legitimacy to bot accounts to be able to inflate upvotes of some posts, but from what I've seen vote-ring detection is really good on HN.