While going through some of the recent controversial threads on HN, I felt that something like this would be a nice thing:

When people mindlessly downmod some controversial but valid comment, some people who stand for free speech and connect with the validity of the comment might want to upmod it more than +1 and show their support. In such cases, the extra upmods should be in the form of karma transfer. It's analogous of throwing your reputation on the line and standing up for someone.