All non-OC posts need to link to the original author's article that introduced the visualization as a link-type post. Merely stating the source in a comment is not sufficient. It doesn't matter where YOU first saw it. You need to find the actual source article. The original source is rarely Gawker, Tumblr, Buzzfeed, Huffpo, or Imgur. Figure out where they got it (Attribution is typically given in the first few paragraphs).
Original source article doesn't mean the original source image. Link to the full page of the source article. This will give the author the credit they deserve, the readers the context they're looking for, and third party pirates don't get hits for stealing content. The official Reddiquette has a good guide:
Look for the original source of content, and submit that. Often, a blog will reference another blog, which references another, and so on with everyone displaying ads along the way. Dig through those references and submit a link to the creator, who actually deserves the traffic.
We believe authors should be credited for their work. To achieve that, we ask that all visualizations posted in /r/DataIsBeautuful link directly to the original source of the work.
Blog posts and other articles that sidestep this by rehosting multiple visualizations from several authors (e.g. Buzzfeed) will not be allowed.