@Silver: I have no idea why he does not get rewarded if she is killed in camp. It seems like the interaction between Wyll and Karlach freezes his journal status, and it will not change if you kill Karlach after (despite her being an NPC still as she has not yet been invited to be a companion).
@Anska: Indeed, the patch seems to ensure that while Karlach lives somewhere in the game (e.g. you killed her, informed Wyll, and then resurrected her like in the Reddit suggestion), you will never meet Mizora. On the other hand, if Karlach is killed and you meet with Mizora during a long rest, you will not be able to use a Scroll of Revivify on Karlach's corpse the next morning.
It seems like bringing her to camp leaves you in a limbo position between the two options, but ultimately, you end up with neither the robe nor Karlach as a playable companion.
