alt Hacker NewsArticle says that it _can_ be calibrated, it just isn't out of the box. So the title seems contradicted by the body.
> If you want calibrated probabilities you’ll still need to recalibrate Jev’s probabilities on your own data. The good news is that is cheap. A few hundred labeled examples from your actual data can be enough to fit a Platt scaling on top of Jev’s scores.
I suspect they meant it as "they claim it is already calibrated, but it can't be, because there is no universally correct calibration", and not "it is not possible to calibrate Jev", but I read it as the latter at first too.