> What problem does this solve that existing reputation systems don't?

To turn its slogan into an analogy: the New Yorker is high quality closed source software. If you disagree with the New Yorker, you can't file a bug report.

You might say, "I wouldn't want to," either because of something on your end, or something on the New Yorker's end. Continuing the analogy, there are closed-source models, open-source-but-closed-development models, and open-source-community-driven models.

I'm typing this because the problem this solves for me is I often disagree with the news, and I would like to fact check them. Perhaps not--as you mention--by calling sources, but by citing other evidence.