To my understanding, it is generally accepted that the primary purpose of karma points on HN is to encourage good discussions. One of the most common reasons I've seen proposed by people who want to bring back visible scores for comments is "it'll make threads easier for me to skim". Another common reason I've seen is "how can I know what I should think without visible karma points?" I feel that it is worth bearing in mind that neither of those reasons is "bringing back visible comment scores will improve the quality of discussion." I also feel that (with the exception of borderline-trollish comments like http://news.ycombinator.com/item?id=2495648 and "Bring back visible scores because I'm angry today!" threads) that discussion quality has improved since comment scores where made invisible, though obviously that position is up for debate. But, if we accept that the primary purpose of karma points is to encourage good discussion (and making, e.g. skimming comment threads easier is at best a secondary purpose), and (for the sake of argument) we accept that making comment scores invisible has improved discussion quality, then it is clear that the correct decision is to keep comment scores invisible, imho.
