Wes gave Davenport the game ball post game, apparently he doesn't give out game balls every game. Said something like Davenport continued to play hard and do the right things despite missing shots.
If Wes says that, perhaps the fans are missing something. One is that the matchup was simply a bad one for him. The other is likely that the rest of the defense wasn't rotating or helping properly.
It's interesting that the +/- reflects Wes's view. I think I'll believe him, even if I saw Davenport get beat with my own eyes. I said last year and continue to think this year that Davenport stands out because when he gets beat, it's very obvious (straight up man-to-man). But I suspect that he doesn't get enough credit for when he does get stops (his man finished 7-19 shooting) or for his help defense.
It's hard to say exactly what it may have been for JD +/- but he did play 31 minutes so the lucky anomaly is hard to argue. I would expect you are correct in that he understands where he is supposed to be (even if he gets beat 1 on 1 some times)...the rest of the time he's not in lala land missing assignments etc. And on offense the same thing...but I would add just his shot making presence opens the floor up a bit for others. You have to stay within an arm length of him out to 25+ ft. He could just stand there and they would have to put someone on him that can't sag.
Plus minus is not an algorithm...it's the reality of what happens when a player is in the game. A lot of different things can affect that reality. Who was in the game with him, did we go on a hot run, did the other team go on a cold streak etc. But over time it can be useful.
I used to love it when STATSHEET gave plus minus numbers for free...with every single lineup variation for the game complete with the minutes they came in and the minute they came out. So you could see what happens when Rob and MAW play with the same 4 other guys. You could see where short scoring spurts were etc. You have to pay for that info now.