The only way I see to satisfy both sides of this argument is to hide the scores until you're done voting on comments for that page. Maybe an "I'm done voting" button at the top and bottom of the page, which removes all voting arrows and replaces them with scores. The score for a comment could also be displayed after you've voted on it.

[The problem might lie in the implementation for this solution. You probably don't want to store the 'done voting on this story' information in cookies, since that's tied to a single device and vulnerable to user manipulation. This means that you need to maintain a list of stories for which each user is done voting in your database, and then check against that list on each page load. This adds a significant amount of server resource usage, as well as maintenance and performance tuning work for what amounts to an unnecessary feature. Showing scores for a comment after voting on it should be easy to implement, but then you'd be encouraging people to vote just so they can see a score, possibly even up-voting everything on the page. My guess is we're stuck with the status quo for the foreseeable future.]