Sorry: about it possibly (and even then maybe as a red herring) carrying into his adult life, but definitely being about the abuse. I wanted to talk about it, see if anyone else had picked up on the clues, but I didn't want to spoil the promos in the title, and the promos are sort of what pushed me right on over to an "uh oh, these ugly thoughts I've been having about Jason just got canonized" frame of mind.
First, we learn Jason was "a stalker photographer", only he wasn't because those were Ali's photos, only he was because Ali should have gotten those things from the NAT Club (Jason). Never resolved. Of course, rewatching all this makes it clearer, but the irony in seeing Ezra come to "save" Aria from creepy stalker, when he's the creepy stalker himself... wow. Note that the notion of "creepy Peeping Tom" carried over into current seasons, too, like Ali's flashbacks yelling that Toby was a creepy stalker (but it was a lie), and of course all the "old guys watching girls" cues, like Byron and maybe that janitor. And of course last season: Ezra's ....everything. But back to Jason, I'm leaning a bit towards those photos being fetishes he's struggled with, is embarrassed of, and needs to find an explanation for. It was just one of those things that never made good sense to me, until these promos.
S2: one of the first things he says to Aria when talking about Mike? He liked Aria's bold fashion statements with the pink hair thing. Yeah: flirting? Or admiring? (I'm not being facetious; rewatch. He's hot, and yet he's awkward with the ladies? And with Ezra? It's just strange.)
Also there was the Ali/Jason weirdness we learn of in S2/S3. Ali was noted as stealing his belongings, but there was always a hint that it was in retaliation for a similar misdeed done by Jason. (I think Alison yelled for him not to go through her things once?)
Ian's funeral: Jason said he was always jealous of Alison. (And once he said he was worse than Ali in general, which made me link up the "breaking into sibling's room" thing). But "jealous" is an odd word to describe their brutal relationship, especially for a guy.
Oh, and the being written out of the will. It's plausible that Granny was pressed about him selling a family heirloom, but ...okay I just don't buy that. You kick someone out of the family for "deviant sexual behaviors", though, indeed! He's like book Emily! I think that would make Granny write him out of the will, and that kind of tension between the siblings is very ..."close to the heart of the show" without twin theories.
The masks were the first "general" evidence of cross-dressing in general for me, some time ago (a week in PLL time). Not the Halloween costumes, but the Alison masks and wigs that made anyone a possible A (or "A team"), which with Wilden and Toby definitely meant A could be a boy, and might have been forced into the girl masks and wigs.
Then finally the intro, with all the emphasis on "pretty" and "little" [waifs] which I'd thought was pure Lolita at first (books and show), but with the show, the intro (versus the book covers) plus Jason's admitted jealousy suddenly started looking like how a cross dresser might fantasize about all those little details (the lipstick, the ...the "girl stuff"). I'm still up in the air as to the "why" of the focus on all the outfits and make-up (it makes up a huge percentage of the books, actually), but I don't know if the intro was just to draw an audience, or to suggest a horny old dude watching every cute young thing in detail, ...or if it suggests someone with a fetish who was jealous of those pretty little details.
Plus the dolls and dollhouses are a pretty big theme, and IMK's the type to make sure everyone knows it's okay for boys to play with dolls. Regardless, whoever A (and A's cronies) turn out to be, those people play with dolls as they're plotting in the episode endings, but WHY? After IMK's AMA saying we're going to sympathize with A, and A is IMK's favorite character, (and IF those weren't IMK lies,) then it's going to be a story that goes full-on tragedy. Crazy chicks aren't going to help me empathize with A; abuse to the degree I'm thinking Jason may have suffered it though? Yeah, I could see it.
For the longest time I thought the alternate choice for A (instead of Alison herself, that is) was Ezra, and then he turned out to be filming girls and worse (raiding panty drawers) much like Jason, and I got pretty SOLD on Ezra having a fetish. I watched for him doing things like, pawing Aria's sweater more than Aria. (And IMK's still got the Hitchcock "evil mom" element there for Ezra, as well. Ezra's not off my radar, though I'd cold pass out in horror if he'd dressed up as his mom.) And if Alison/Ezra were never a thing, what's with the giant posters of Alison in Ezra's lair? Obsessed Humbert Humbert, or a Bates boy?
I could go on; will leave it at, "it seems to be a theme". But again mostly, Jason still going on about being jealous of Alison (promos) just really did me in (where I wanted to open a thread and discuss if anyone else had picked up on it).