This is no better seen than when Israel/Palestine articles hit the front page. You can nearly watch in real time where a critical mass is reached and suddenly pro israeli comments start flooding in. It's a thing of beauty to watch.
If you look at the /r/videos subreddit you can see videos uploaded showing clips from the official ellen page which arn't particularly interested but have been boosted to the top and are full of comments talking about how great ellen is.
Even subreddits that have failed to reach the large member volumes other subreddits have are not immune to this manipulation.
It's unfortunate because it stiffles original dialogue.
Sometimes I wonder what would happen if reddit got rid of the upvote button and only allowed posts to be down votted. Articles and comments which survived the war of attrition might be a little more inciteful.