A more general form of tutorial review/correction site would be more interesting. Actually, a browser add-on to load commentary/annotations for known tutorials

A more general form of tutorial review/correction site would be more interesting. Actually, a browser add-on to load commentary/annotations for known tutorials on the fly might be nice. All sorts of practical problems that would have to be overcome, though (like changing content and getting people to use the add-on in the first place).