These extra features could help it narrow things down more quickly, but CF doesn't need any of this to get good quality- what I described needs _no_ features, o

These extra features could help it narrow things down more quickly, but CF doesn't need any of this to get good quality- what I described needs _no_ features, only the observation of interactions between users. It tries to find a pattern to explain the successful interactions, by generating a set of features for each user and optimizing it to fit the data.