That's the other thing that's been proposed. I've always felt that doesn't seem like an elegant solution to me. The act of the button's disappearing once you've clicked is a response enough for me. It also serves as a visual cue of what you've read and what you haven't.
The question I'd ask you is what matters more, the discussion or the moderation? Shouldn't the attraction to the people commenting here be the quality of the conversation, rather than the ability to vote things up and down? The latter is important, but does it have to be seen?
I agree, it's a pretty elegant solution. However, I like seeing how many points a comment has, before I vote, for several reasons:
* I often don't vote
* to see how, exactly, the community feels about it
* to see if I should actually read it
* to get a feel for the story's exposure (more votes, more eyeballs)
This wouldn't be an issue if it weren't for the first point... I don't want to have to vote on each comment to reap the benefits of the other items on the list.
The second item on the list allows me to have the "blink" effect. By taking in the vote #'s of hundreds or thousands of comments, I just get a "feel" for what HN likes and dislikes. To me, that's it's important.
I think something in between would be a color-coded and/or normalized indicator of each comment's popularity. Kind of like how the grayed out text is more intense for more downvoted comments... upvoted comments could have some indicator of how popular they are.
If normalized, it would show how popular they are, but only relative to other comments with the same parent as them.
The question I'd ask you is what matters more, the discussion or the moderation? Shouldn't the attraction to the people commenting here be the quality of the conversation, rather than the ability to vote things up and down? The latter is important, but does it have to be seen?