I have yet to meet any adult in real life who has been harmed in any form from believing in Father Christmas as a child.
I can understand that if relatinships within a family are already strained then the FC thing may be built up as one such issue - perhaps.
But tbh I know so many people who are perfectly happy having found out at some point the truth behind FC, and none have ever felt their parents were wrong or lying to them.
I can't believe there are any parents out there who have never ever told their child a lie - even if a tiny small one. Most of us do it most weeks - "Oh, it won't hurt" "it'll do you good" "it's goof for you" etc.
Fine - if you don't want to do the FC thing for whatever reason - but to say that those who do are omehow doing wrong byt he children - well, nonsense!
DD is 9y. i don't think she really believes tbh but she will play along. She likes the magic and the idea of it all. But over the last 2 or 3 years she had asked questions or made comments that makes me realise she has worked it out. I have never told her he isn't real, but I tell her "what do you think?" and she is happy with that.
I was nearly 10y when my sister was born. As a teen I knew the truth but I always played along, and really enjoyed doing so, for the benfit of my little sister. I never once thought of spoiling it for her.
A bit of pretence and magic is not a bad thing in life! I thinl we all could do with some of it sometimes no matter what age we are.