In general, I believe that people posting only the content from a source and having no further opinion of their own, should also be punished, maybe a warning.
Per current available rule, depends on the content quality, only two possible solutions
- Move it to trash can (if content quality is low)
- No action if content quality is good enough. At least it does not break rules but I agree that anyone share content should add his/her own opinion about it. It leads to another issue, how to judge the his/her opinion is acceptable enough or simply write one short sentence to regularize it to avoid trash can