When I evaluate the merit someone's statement in the real world a big factor will always be my and others' respect for that person based on my his\her reputation.
The comments on HN already display the user name. Tell me, would you honestly discern a comment from pg the same as you would for some other unknown user?
To be honest, I don't usually read the names of those commenting (and notice that they are less prominent, being in grey, than the comment itself) - at least until after thinking "Good point, well made."
I don't buy into this whole pure non-contextual ideal, as though the only possible result of attaching a name and a reputation to a comment is an ad hominem argument or fan-worshiping.
When you're making an argument or counterpoint, you would do well to divorce your argument from the external characteristics of whoever you're responding to. However, when you are just reading through conversations for your own benefit there is a lot you can gain from the added context of the user's reputation.
For example, whenever there is an article about security and I stumble upon a comment written by tptacek, I can safely assume that he knows what he's talking about and I can therefore place more trust in his comment than I would in a comment from someone I don't know. This context is particularly useful to me when I have a hard time judging the value of the comments alone simply because I know jack squat about security.
Similarly, if I stumble across a comment that makes a radically strange conclusion (like "women and men should be lumped into one sports category") and I look at who wrote it, I can remember that the commenter has made some very good points in the past and is not prone to making dumb arguments. From there I can cut a little more slack in my own mind for the argument and I can try to reach into it and see what the main point he's trying to get across is.
None of these approaches is fan-worshiping, nor do they involve me making an ad hominem argument. Context is absolutely useful for humans. We are inherently biased creatures for a reason. We have to make quick judgments and take shortcuts every day to deal with all of the information, and the context of others' reputation works great for this.
You wouldn't do a risky business deal with someone whose reputation you didn't know, would you? Well think of reading others' opinions as a kind of transaction. You take on a little risk by buying into someone's opinion. You may change your worldview just a tiny bit based on the value you place on another's comment. That is what conversations are all about. The risk comes from the possibility of adding inconsistencies, falsehoods, or improbabilities to your worldview without realizing it. We don't know all there is to know and so we cannot make perfectly objective and absolute judgments on whatever we come across.
Philosophically, I largely agree with you. The problem is raised by the fact that karma is largely a measure for "how long have you been on HN?" rather than anything that a sane person would like to base their opinion on. This is most clearly evident in your example with tptacek; could you tell me how you would go about determining his aptitude in the security field by looking at his karma score?
Oh I absolutely agree. Karma is definitely little more than an odometer and not useful for reputation purposes at all outside of an individual comment, and even then it doesn't say a whole lot.
Are you going to base your disertation at "argumentum ad hominem"?
No to the subjetivism