Clearly competent moderators have some sort of effect, or these stories would not exist. If self-moderation worked, then the dangerous canning post mentioned in the article wouldn’t have gained any traction.

Without competent moderation, the ability for users to manipulate or derail communities grows. A voting system is entirely subjective, and a bad or dangerous idea can set roots if enough unaware people give it the votes. I am aware that moderation is also subjective, but competent, knowledgeable mods can help guide a community, or protect it from targeted harassment.

Also, they’re the ones with no life who can devote their time to monitoring the community. Most people spend a few minutes at a time visiting a community. That’s not enough time to verify every post in the last 24 hours, and vote for them all accordingly (depending on the size of the community of course),