I'd say hierarchical credibility. More authority. Give the leaders power to bless others with disproportionate power, who in turn have the ability to bless others with disproportionate power.

Remember that Reddit ultimately only imparts one vote per person regardless of whether you're an admin or moderator or whatever. End that system. We've already established that these systems are not libertarian - the leadership has an opinion (in /r/Science the opinion is that you must post good science) and we want to empower them to enforce it.

Not only that, but provide negative feedback. If you endorse a terrible person, make it impact your credibility.