"Why wasn't I consulted,” which I abbreviate as WWIC, is the fundamental question of the web. It is the rule from which other rules are derived. Humans have a fundamental need to be consulted, engaged, to exercise their knowledge (and thus power), and no other medium that came before has been able to tap into that as effectively.
The obvious example of WWIC at work is Wikipedia, created for free by unpaid labor. It tapped into the basic human need to be consulted and never looked back.
Adding voting, and voting of comments, is the best way to ensure that everybody is consulted about as much site content as possible. It also helps alleviate moderation problems because users enjoy and see it as their duty to moderate content.