[Keneldil the Polka-dot]

I think that if the request besmirched Thingol, it probably tainted Beren too.

I don’t think it was the request that besmirched Thingol. He named the Silmaril as his price for Luthien with the thought that the quest was impossible.

And those that heard these words perceived that Thingol would save his oath, and yet send Beren to his death;

And if there were hope or fear that Beren should come ever back alive to Menegroth, he should not have looked again upon the light of heaven, though I had sworn it.

I think the fate of Doriath was sealed after Beren actually returned with the Silmaril.

Beren’s motovation had nothing to do with possessing a Silmaril. I think that is why he did not fall under the doom of Mandos, not because he wasn’t an elf.