[big_curses]

I'm not the person you asked, but I could see there being harm in lying to children about how reality works. When children are first growing up, they have no clue about the nature of reality, of what is and is not possible, but their brains are constantly gobbling up data on what the world is like. From this, one forms concepts of how things relate to each other. Ideally as they do this, there are no contradictions between their concepts, or they're worked out over time, but in lying to a child and feeding them this false information, you are introducing contradictions into their concepts and distorting their view of reality. And one's view of reality directly relates to their ability to interact with it in a self-beneficial way.

Now I can't say that this will actually have much of an effect, like I said, we can naturally work out these contradictions over time, but I think this is why one should not lie to children in general.

Like you say, not all untruths are created equal. It could be quite easy for them to fix their concepts once they realize it is a lie, but perhaps it could have some lingering effects. I can't say. I'm not a psychologist and each individual, and their mind, is different.