It's useless for a one game analysis. This game is the perfect example of that. That's why it is so weird that CMP would choose to use that when describing how well Morton played. As I said before, he could have used several examples of Morton's play to explain why he thought he played well. No argument there from me. But as soon as you try to use +/- to make your point either negative or positive when evaluating 1 game, it loses credibility.
No one can possibly look at those numbers from that game and say that they accurately measure how guys played in that game either good or bad. Does anyone think that Jones "deserved" a -14? Of course not, and neither does CMP. He would never say "Jones played poorly today, look he got a -14". That would be ridiculous and so is the +17 for Morton.
For the record, I think Morton gave us exactly what we need from him in that game. Not a ton of minutes, but enough to give other guys a break. Move the ball, play as good on defense as he can and don't turn it over. Mission accomplished. Just don't use the +/- stat to say he played well, it ruins the argument of his value.