You've created a bit of a contradiction here by assuming that the quality of content can be determined objectively in the first place. Quality of content is inherently subjective because there's no definitive "perfect quality." A research paper might be extensive and carefully written, but that doesn't mean that it's better content that a wellcrafted joke- a lot of people would rather hear the joke, which gives it subjective quality. The point of an internet community is to align yourself with others who have similar subjective views on quality. If you want jokes, follow a joke page. If you want papers, follow an academic page. The voting system within those pages determines the quality of posts within their subjective viewpoint.