I have just noticed that in many online communities, you couldn't easily filter on extremism because, based on the community values, expressing the wrong opinion is "trolling" but responding to that opinion "die in a fire you fucking asshole" is a top-rated comment. I don't even think these are outliers, a lot of communities are run like this.
Also, possibly this comment would be a false positive in some places because I included extreme text as an example.