This is a cool idea. I would install a Chrome extension that shows a score by every username on this site grading how well their expressed opinions match what subsequently happened in reality, or the accuracy of any specific predictions they've made. Some people's opinions are closer to reality than others and it's not always correlated with upvotes. An extension of this would be to grade people on the accuracy of th…
Of course in the above example of stocks there are clear predictions (HNWS will go up) and an oracle who resolves it (stock market). This seems to be a way harder problem for generic free form comments. Who resolves what prediction a particular comment has made and whether it actually happened?