Post characterization (Rewarding great posts, and identifying bad posts...)
Post Reaction Let everyone moderate! Vanilla forums allows a reader to have a "Reaction"[1] to a post along the lines of: Promote, Off Topic, Insightful, Disagree, Agree, etc. There is a way to curate the forum based on aggregate reaction.[2] Of course if every user has access to create a reaction to every post... this in itself can lead to abuse.
Random Mod Authority Make moderation a desired privilege! Slashdot (remember the glory days of Slashdot? No? Right... I am old) used a moderation system[3] that allowed semi-random users to characterize a post as Offtopic, Troll, Redundant, Insightful, etc. If a post got enough "troll" clicks, it became less visible, if it got a lot of "insightful" clicks, it became more visible, etc. By making the ability to characterize a post somewhat random, they avoided common "rep my friends, dis my enemies" type abuse.
Earned Moderation Authority Another way of making moderation a privilege. Stack Overflow and of course Discourse (same devs) use a more complex system of Increased User Reputation = Increased Moderation Power. This has its own weaknesses as the appeal of moderation power is high to certain people and low to others. It does, however, have wonderful spam mitigation side effect: its just too much work to spam.
[1] http://docs.vanillaforums.com/help/reputation/reactions/adding-and-editing-reactions/
[2] http://docs.vanillaforums.com/help/reputation/reactions/curating-with-reactions/
[3] https://slashdot.org/faq/metamod.shtml
