In fact I will go as far as to say that the ideal interface would be one that let me specify what the ideal score of every comment should be and my vote should be counted as an upvote if its below that value and a downvote if its above that...
Yes I've had this idea before too. I also think that the votes should be applied to the score in reverse order of the time at which they were made. This means that those who vote earlier end up having more effect on the final score, rather than none at all, as would be the case otherwise.
That would be a star rating system then. Supposedly they work worse.
No, star rating systems generally average. The GP's proposal is not the same.