It's to Joker's advantage that he's an old enough hand at this that his emotions don't betray his intentions. Steven can sense some of his general feelings, but none of it spikes enough for him to make anything of it. Lack of proof either way is the best thing he has at the moment.

It seems odd to smile at someone casually acknowledging your plan to end the world, but that's what Steven does. It's small and frail, but acceptance is something he's craving right now.

"...Won't the carnival get mad?" he asks. It won't matter for long, but it might result in more of them coming to harass him, which he is sick of.