Fundamentally, the problem with the site is that Reddit was happy getting growth on the back of people searching for jailbait[1] and creepshot porn and white supremacists for years and they have a user base that reflects that. A lot of the power mods that run the largest subreddits are just awful human beings. I don't see how they fix that short of nuking the whole site from orbit and starting over.

[1] http://web.archive.org/web/20110429125747/http://www.alexa.c... (check the top search terms)