> The font-color of the comment (aside from links already visited) should be enough to indicate... Yes, this is true. However, consider a comment with 0 points

> The font-color of the comment (aside from links already visited) should be enough to indicate... Yes, this is true. However, consider a comment with 0 points. If two HN visitors see it at roughly the same time, and both upvote it, it will have 2 points, rather than one point. What's more, neither visitor will see the effects of their action until at least one page reload and some time has passed.