Pasting the entire contents of copyrighted material is illegal. The top article on HN right now is about plagiarism. What you've done here is literally a crime. Please don't put Y Combinator in this kind of position.
Further, YC is protected by DMCA safe harbor provisions.
> by the distribution of a work being prepared for commercial distribution, by making it available on a computer network accessible to members of the public, if such person knew or should have known that the work was intended for commercial distribution.
The Wall Street Journal has a pay wall and the parent posted the full contents of the article on this site.
Regarding safe harbor, YC must comply with any take-down notice to be in the clear. The safe harbor does NOT mean that YC gets a Betamax-style free pass when users upload copyrighted material illegally.