I realize this thread has been done to death, but I wasn't around at the time and I just have to ask:
If an aluminum gnat consumes aluminum but doesn't burn it, would she be immune to emotional allomancy? It seems like anytime I've seen this thread crop up, people get hung up on the investiture side of the argument and forget about the curious property of the metal in and of itself. When Vin and Kelsier reach for their stores, it's very much described as them probing around in their mind and finding a trove of power. It makes no sense to me that an aluminum-lined hat would shield you from emotional allomancy, but aluminum that is in your body and producing a reserve of investiture-draining spiritual power in your mind confers zero advantages.
Does an aluminum gnat generate atium shadows if her aluminum reserves are full? I'm sure any answer to this question is likely to be inconclusive speculation, but it's something I've been mulling over ever since I stumbled over the part of the Coppermind that lists its properties.
Another thing I've noticed is that Sanderson pays a lot of attention to the ability to push and pull with a light touch, as well as to be much more discriminating about what you are pushing and pulling in any given moment. Kelsier marvels at how Gimmel can burn iron to make metal objects drift gracefully into his hand, Wayne can use a kind of allomantic precision to modulate the size and placement of his speed bubble, Wax can create a soft pulse that pushed out at all metal objects except a few specific items, Breeze can finesse his Soothing in ways that make others marvel at his sheer talent.
This really got my noggin joggin', because in the books, even though the index says that aluminum burns all your reserves instantly, the effect isn't actually instant. When Vin burns it, she can feel her Pewter reserves draining. In the Coppermind, it says that aluminum burns invested metals first. Why shouldn't someone who was just very gifted in the use of aluminum be able to invest just enough aluminum to drain her reserve(s) very, very slowly? And what would such a person be capable of in that state? Would this person be able to temporarily stop herself from generating atium shadows? Would she be immune to emotional allomancy? Would she disrupt speed bubbles? Would it be harder to push on metal she happened to be wearing or holding?
Just a few thoughts I wanted to add to the discussion that I hadn't come across when I looked. I realize this is a bit disjointed. Forgive my enthusiasm.