"GDEX tracks how many times a game is mentioned on social media, but it also looks deeper. We look at the sentiment of conversation. Say something nice about a game and it will help the score increase; slam something and the opposite happens."
This is BS. The sentiment analysis you can wring out of a 140 character tweet is so fraught with error, it's not even worth doing. If you say "This game definitely does not suck." that would probably be counted as a negative sentiment. And even if they explicitly include "not suck" as a positive parameter, there are countless others.