If you reply to this post, I'm gonna assume you're cool with TWEWY spoilers. If that isn't the case, please let me know
over here, and I will automatically assume I don't have permission to do any of the things listed on this post due to the spoilery nature of Joshua's special permissions!
Ranked in order of likelihood:
1) Is there something odd about your character's soul? Joshua can sense things about characters' souls and Imagination. Because those are rather vaguely defined in canon and things in Vat don't quite work the same way, just tell me if there's anything unusual about your character that Joshua would potentially be able to sense. Is your character strongly connected to spirits? Is your character an angel or a god? Is your character dead? Are they missing their soul? Is their soul shoved in some random inanimate object rather than their body? Let me know!
2) Can Joshua read your character's thoughts? Joshua can casually read the surface thoughts of people, but generally isn't going to go any deeper. Are you okay with Joshua potentially reading your character's surface thoughts and possibly knowing their name before speaking to them? Can your character detect and/or do anything if Joshua decides to take a peek at your character's thoughts? For mind-readers who decide to turn the tables on Joshua and try to read his mind, be aware that he can show you what he wants you to see rather than his true thoughts.
3) Can Joshua imprint on your character? This is unlikely to happen in game but... Joshua can make certain keywords/ideas appear in peoples' thoughts, but he has no control over what they will make of the idea. E.g. He can make a person suddenly think about ramen, but the person might decide they don't want to eat ramen, or wonder why they suddenly thought about food in the first place.
4) Can Joshua mess with your character's memories? This is highly unlikely to happen in game but... Joshua can take away memories, as well as return them in varying levels of completeness (i.e. he can withold parts of a memory). Basically, when he takes away a memory, there'll just be a blank where the memory was; he cannot replace memories with fake ones. Are you okay with having your character potentially having their memory messed with? Can your character detect/do anything about it?
1) Is there something odd about your character's soul?2) Can Joshua read your character's thoughts?3) Can Joshua imprint on your character?4) Can Joshua mess with your character's memories?