I agree with Miyabi, if it's going to limit anyone's power, it's going to be the person who burns it. It doesn't seem fair that if I burn the 15th metal, I get allomancy, and if I burn the 16th I get to trap a god. That's just not cool.
So, what if the 15th metal that Elend ate (small crystalline piece) was a crystal that had solidified out of the liquid metal pond/lake. Elend gets allomantic powers because it's the metal that is involved with Preservation. Then, the liquid metal lake would be made of the 15th metal, and the "clear metal" in the well that Ruin was in would be the 16th. (Not the 17th and 18th). So, if this is the case, would someone gain allomantic powers by ingesting the liquid metal or just the crystals from it? And what sort of powers would they gain by ingesting the stuff from the well of ascension? Hemalurgic powers? Those associated with Ruin? Would you get crystals from the "clear metal" within the well? If so, where are they? Could this be where Vin's going to get hemalurgic powers from? Or does she already have them?
I pretty much agree with this. I think that the 15th metal could well be from the preservation-lake and the 16th from the ruin-lake. And Miyabi, we absolutely have evidence to suggest this is a way to get hemalurgy through allomancy. It can be inherited genetically, or through the 15th metal. So, hemalurgy could be inherited through piercings, or the 16th metal. Which would explain how the LR is a hemalurgist for all you die-hard "the bracers are not hemalurgical" people out there.
I think we can assume it's something new, since Ruin can alter text and metal minds, and none of the human magic systems can do this.
Not necessarily. We don't know for sure what they're capable of, and even if we did, it's possible that Ruin just has the subtlety of millennia of practice. It's kind of like how inquisitors see. Maybe moving ink around is just very subtle allomancy. And we pretty much don't know anything about hemalurgy.