Death portrayal

[Kath]

Well Ar-Pharazon I'd say that was a pretty good second post! But I wanted to comment on your final point.

did PJ make the mistake of using Gandalf to describe mortal death as the immortal's description of the passing into Valinor?

I think that Gandalf's description was all he knew, and that his words were more to comfort Pippin at the time than actually contain genuine knowledge of what was to come.

Although, Gandalf did 'die' after fighting the Balrog in Moria - so maybe he does know what is to come - and is telling Pippin the truth. Because at that point he would not have been passing into Valinor, but dying a (sort of) mortal death.