(don't you hate it when answers are unclear, or contradictory)?
The uncertainty comes from the fact that the information you gain from the meter reading will need to be interpreted with the effect of a polarizing filter in mind.
To understand this, I'd suggest an experiment. With the filter in place on the camera, take a number of meter readings, each with the polarizer set at a different position on its ring. You should see variation in the readings, because the polarizer tends to filter out the polarized light reflecting from the scene. You have to consider, however, whether it is the polarized light portions of your scene that you want to key into when you are choosing your exposure. In many cases, you are most interested in the other parts of the scene.
So which of the various meter readings do you choose?
If you meter separately, without the polarizer in place, and then apply the standard filter factor, you will get consistent exposure of the parts of the scene unaffected by the setting of the ring on the filter. That may lead to better results.