oh 100%. i think a lot of people believe in the misconception that peeta has been "brainwashed" or something when that is simply not the case. he's essentially been conditioned using negative reinforcement and psychedelics to view katniss as a threat and fear her, and even then they were only able to alter his perception of certain memories; they didn't wipe his identity and replace everything he's ever known.
i think a lot of this characterisation is shown through his interactions with other characters, not necessarily katniss herself, however, and that's where a lot of people start to spiral that he'll never be his old self again.
during the weird scene in the cafeteria when he lowk threatens finnick about annie, that's him trying. he's trying to be funny whilst also being protective over his friend. problem is, cf and the quell era in particular are probably where snow got a vast majority of their content for the hijacking, and guess who's a part of a vast majority of that time period? oh, that's right. myshayla, finnick. so peeta's weird tone? his joke not coming off quite right? his generally uncomfortable behaviour? yeah, that's cos he was probably tripping balls ab finnick and katniss—two live triggers sitting directly in front of him. but what i read as the bottom line of that interaction (as awkward as the situation is) is that he genuinely means well for annie. and that's the old peeta shining through, even if it's poorly executed by his recovering self.
he's good with delly too, as long as the conversation isn't about katniss, even when he's very freshly hijacked. and in the capitol, he's so damn charming he makes pollux smile in the place of his imprisonment and makes tigris blush in spite of the fact they're on a mission to assassinate her cousin🥹 (yes, ik snow is awful and evil. but there was a time when he was coryo to her. i don't think she had any second guesses ab the fact he needed to die, but that doesn't mean it was easy.)
his return to katniss is more gradual. remembering her favourite colour is green. her favourite food is lamb stew. even the nights on the train line—it's delivered in a completely unhinged way, that's still him remembering intimacy with her that remained out of reach for snow.
and then there's bigger stuff. i see a lot of people overlook the fact that he's the one who lifts her to the ladder in the sewers and forces her to climb the ladder to safety. this is a very direct parallel to their first games: fleeing from mutts in a gamemaker-manufactured scenario, peeta ushering her to climb, worrying about her and her safety before even considering his own.
if that's not his old self, idk what is.
granted, he does have a hijacking-induced freak out afterwards, but as soon as he does, he tries to do his age-old strategy of pleading with her to leave him and let him die if it means she can get away. and when she doesn't, when she instead kisses him shows him the first real glimpse of affection since his torture, he gains back even more of himself—he remembers his promise of always.
i'm also a firm believer in the idea that peeta rescued katniss from the firebombs. if he was far enough back to escape the pod where the street caved in (mind you, katniss and gale barely made it and they're extremely fast and have their two original legs—i reckon peeta had to have evaded it entirely), he would've been far enough out of range to escape the worst of the explosion from the bombs. but instead, he's a "fire mutt" like katniss, covered in burns. the likelihood of him receiving those burns from several hundred metres back is insanely low. but if he walked into the flames himself? different story. just saying.
and all of that is right before he stops her from killing herself because no matter what, he can't let her go.
even katniss phrases it as peeta coming back to her when they grow back together. not rebuilding his personality. returning to himself.
i think it's stupid to say he's the same person he was before the war. that's not true for any of them. BUT i mean that as in he—and everyone else—has been through a major trauma, not that he is irreparably damaged by the hijacking. i'm so fucking tired of hearing that he "falls in love with her twice" or that "he'll never love her the same" like please bffr. he doesn't forget his feelings. that's the whole problem. that's why he's so damn confused.
anyways, i'm moving away from my point here, but basically, yes, peeta returns to his old self, at least for the most part. just with a dash more of ptsd.