This is a minor theory.
At his death, Miles gives what sounds like a death rattle. I propose that this has nothing directly related to Moelach or the influence of a shard. Rather at the moment of his death he was burning not only feruchemically charged gold, but uncharged gold as well. (Maybe he instinctively drained a gold metal mind instead of burning it, then inadvertently burned it for gold allomatic effect.)
I think that looking into the spiritual realm by allomatically burning gold at the moment of death would be enough to trigger a death rattle.