I think if one were to try to sue them, one would have to mount an attack along this vector. The editorial nature of their review system could be seen as a generator of new content (even if it is based on used-submitted content); the end result (in terms of message and tone) is considerably different to the initial material.

I wonder though if such an approach has any legal merits. I've heard of something similar with copyright, where aggregating data for example and presenting it in new ways is copyrightable. I think one could expand upon that approach and use it as a basis for the complaint.