This point still confuses me. He quite handily puts Kelsier on his rear in The Well.
So he can harm someone if he's provoked? Or is it because he knows that regardless of what he does to Kelsier it won't actually harm him?
And a lot of "harm" is in the mind. Even without a corporeal body, it would still register as pain, thus harm?
And wouldn't it still be considered physical harm, if Hoid was there physically? Applying physical harm?
Brandon Sanderson
If you re-read that scene, Hoid himself is shocked he's able to do what he does there. Let's just say he himself doesn't quite understand the issue as much as he once assumed.
ice_royale
Can we assume he cannot harm a LIVING being, but Kelsier is at that point not a living being?
Brandon Sanderson
This is the conclusion Hoid came to, so it's a pretty solid assumption.
Dawnshard Annotations Reddit Q&A (Nov. 9, 2020)
I don't think Brandon uses assumption on accident here. I think it is an assumption and a big one.
So its definitely an external entity's(Ruin/Destroy) perception on a spiritual level, and also cephandris's perception of himself as being unable to destroy because he bound that part of his spirit web away in night blood. Then on top of that you have them being in the well of ascension. The very place where Ruin in a cognitive and spiritual sense only was trapped for at least I'd say 3-8 thousand years, just permeating the very location in his essence on the cognitive realm.