DAFR
Wait...why should he tell her that secret? It's not like it's something sinister. It's not like its his plan of world domination. At the very basic level, he was hiding his advanced studies, it's just that he advanced those studies beyond anyone else that Luna knows. Additionally, the whole "wandless-magic-works-like-this" thing can be called 'family magic', as it was created and advanced solely by Harry. And every family has its secrets. From blackmail potential, to esoteric magicks that are advanced than what is available to current public. Harry didn't betray her or anything. He more than likely protected her from possible hounding of greedy wizards that wish to rip out secrets of others, like Voldemort. Do you not think that if Voldemort knew of Luna's knowledge of Wandless magic, he would send parties to retrieve her, so he could add the ability to his own already impressive repertoire? Harry is protecting people by not making them targets. Unspeakebles would abduct people if they knew of his capabilities.
I hope Harry will show his displeasure at Luna and her secrets, and her hipocrisy. I hope Harry will show that a relationship, a working one, should have trust going both ways. Plus, why should he tell her all of his secrets? He doesn't know if she won't be mind raped or blurt out it accidentally, like in so many other fics. Yes, fidelius does protect it, from that, but it can be broken, and bey bey "low-key".
Yeah disappointment is the only thing im feeling right now after ahe learned his so called secret she throw him away like a used con*dom what will be her reaction if he choose to dont say anything after so much drama and being loner for 14 years you still fack him up i mean your novel font have 1 decent woman to support him you have turned all villains and tour mc dont have any pride? is he still the one who play dumbassdoor and voldisorts by the nose? Is he so desperate to gain a friend to tell averything and being throw away? At least use oblivate you know how many ppl can gain his secrets out from luna after her emotional stability? He still have courage or cunning or wits because after that i dont see any of this quality's in him just sent him in a corner to cry and draw circles other reincarnated mc's by now have milions of money and even if he hasent a bussiness tycoon he can still know the future to invest ffs he have time tuner he can win the lotterys he can have as many friends as ge wants and he is a brooding looner with no gf just another beta with no courage and ambitions and dont ask me about the wits forget them slytherin ? He is a freaking hupplepoof
Honestly this is way too unnatural. Literally everyone has secrets and she is literally flipping out on smt that simply is non of her business. Plus, why are you trying to vilify the fidelus charm? Its not like he mindraped her or did dark magic of anything, this charm is used both in canon and fanon and your making it sound like your talking about crucio instead of fidelus