One thought is that maybe the score gets hidden if it is 1 or less. I think that scores are especially interesting when it highlights a great comment or provides feedback to the person making the comment.
The ordering of comments without a score is a good example of why a visible score is needed. You assume that the best comments are on top but it is not clear how good are the comments below the top one.
Since the scores were removed, I have been commenting less often and often ignoring many of the comments below the top ones.