You could give everyone a unique identifier per thread.
For instance, the ggp is a security professional. I give more credence to his opinions than others.
On the other hand, when somebody who is deeply respected (be it pg, or any prolific high-karma commenter) posts on something where they have no particular expertise the comment shouldn't get special consideration due to the author.
I can't think of a way to reconcile these, and there's enough people who post here that are actual authorities in relevant areas that I wouldn't want to give up the first. Being able to know that, say, a comment about security was written by tptacek matters more to me than "oh look, pg made a two-word post that got 9001 points".