You mentioned at some point that during Mimicry, the mimic's true voice went from being mean to Mark to being mean to himself. Can the humans (or anyone other than the mimic itself) "hear" that? That'd make things later a bit more interesting. M!Cesars true voice with be saying stuff like "Mark doesn’t love me :,(" and Mark will be like "Why is it using the scary voice to whine about things now?" 😕
I'd describe it as less Mark hearing the voice as anything solid and coherent as it isn't being directed at him, and more that he can pick up on some intense emotions/thoughts that don't belong to him. True voices are a bit weird and hard to define in human terms, but the general gist is that they can't usually be understood/heard except when a mimic is sharing them with a specified target or victim!