If it's ever readded, they should replace the actual mental disorders with the weird things about the game.
Some NPC could describe the horrific experience of hallucinating a pirate appearing from thin air in York Town after being hired by the guards there. Another could be an NPC who was a former teacher in Onnet Town who told students that if you cut down a bush it doesn't grow back, and if it did it certainly would take much longer than mere seconds. Another NPC could claim that railroads were stolen from the future. An NPC that went to sit down at a night club and all of a sudden was teleported to a secret VIP room.
And you avoid actually stigmatizing mental illness in the meantime.