Your point about valuing an opinion more highly from a person who is known to be accurate on a subject is valid. In the arguments case, I think it's easy enough to follow an A/B conversation, even without names.

In the first case though, it still seems that the majority of comments here are not so specialized as to require the posters identity to determine if the content is accurate enough or not. Ideally, if you could not judge the accuracy of the comment on your own you would leave it alone. There would be enough others that could judge it impartially that the comment itself would get voted up or down appropriately.