This thread is bait, but I am going to write out a serious response so I can point to it every time this comes up in the future.
I run a forum that has a rating system, like Facepunch. I also lurk Imgur, which has an up/down rating system a la Reddit. The main benefit of having ratings in my forum is that it sends more tactile feedback to the users about how their post was received. If you say something really agreeable or informative, there are agree and informative ratings. If you say something dumb, people can rate it dumb or autistic. This has solved a problem where people thought they were much funnier and well-liked than was true would make stupid posts all the time.
Imgur does something similar, but much more brutal. Any post that gets downvoted is basically hidden in the single-threaded comment block, or even hidden completely in a bad comment section that you have to manually open to see. Often, these "bad" comments are just unpopular opinions. If a front-page post is something like, "As a Christian, I have no problems with gays getting married and transgendered womyn adopting!", and you reply "As a Christian, the bible tells me that being gay is an abomination", your post is hidden. It's basically discarded because it's not popular enough.
And that's the problem with these systems. Reddit and Imgur are great at content aggregation. They are not great at having a discussion. My forum's rating system is good at informing people what others think at them, but it encourages mob mentality and homogeny in the community.
Imageboards are not about content aggregation and they are not about popular opinion. If anything, it's the exact opposite. It shows you things you don't want to see and it tells you things you don't believe in and don't want to hear. Every idea is given equal merit and equal real-estate and no amount of collective ass pain can take that away (unless it's a mod~). This is why boards like /christian/ do well on 8chan; religious conservativism is a minority on the Internet now and they'd probably be banned from /r/Christianity for "making the rest of them look bad".
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