Not literally, literally, but it’s kind of a running theme, and there’s two ways of looking at it. Here’s one:
Starting all the way back with her chronic narcolepsy which was retconned as to be Vriska’s fault (because the best way to have a disabled protagonist is to retcon away the disability).
After Cascade, she spent three in-comic years (and a real life year and a half) on the boat to the Alpha session, during which she didn’t really get a lot of focus.
Once she arrived in the Alpha session, she was immediately possessed by the Troll Empress.
Then a house falls on her and she dies
Then there’s the retcon, and in the new timeline Jade is still on the boat but now John and Davesprite die pretty much instantly and she has to be alone the whole time.
Then she arrives at the alpha session, and is immediately possessed again offscreen, before being put to sleep by Vriska.
When she finally wakes up, she sees a note telling her to take care of Bec Noir and PM. She tries to get them to stop fighting, but PM punches her out and chops Bec Noir’s arm off to defeat him.
To give a sense of how disconnected Jade gets from the rest of the cast, she and Rose are the two main female protagonists, and in the post-retcon continuity Homestuck ends with them never having a single face-to-face interaction (a streak yet to be broken onscreen in the epilogues or Homestuck 2!). This incarnation of Jade has never heard Rose’s voice.
Jade doesn’t get much focus in the epilogues, either version, and gets possessed by Calliope, which lasts into Homestuck 2.
That said.
One of the reasons Homestuck’s bullshit is worth putting up with is the gulf between what it’s about and what it’s about.
Davepetasprite straight-up explains the themes of Homestuck to Jade: Everyone has different versions of themselves, which they often don’t like, but the true, ultimate self is the sum of all these parts, and once you understand that, you have the power to be free of your ordained role and can do what you want. The epilogues take this super literally, with the Ultimate Self being a Super Saiyan God Super Saiyan thing. But take a step back.
Self-loathing is a major recurring theme in Homestuck. Everyone deals with it, and thanks to the sci-fi premise of the story, characters are able to literally face, confront, and beat the shit out of parts of themselves they don’t like. Jade hates parts of herself. She hates how much she just wants to fuck around when there’s serious stuff to be doing. She literally kills this part of herself in order or save John in EoA4, and then spends all of Act 5 in srs business mode. Act 5 Jade Harley is no-nonsense, goals driven, and a successful 1980s businesswoman who does all her quests like she’s supposed to. And she’s not a joyless robot during Act 5 or anything, but there’s a very clear distinction between the Jade Harley of Acts 1-4 and the Jade Harley of Act 5.
And her possessions, deaths, KO’s, and other get-out-of-the-plot-you’re-too-powerfuls of Act 6 could be seen as a continuation of this trend, metaphorically. From a “very silly girl” to a take-charge plan-focused leader to someone who never gets to have fun with her friends because duty keeps calling. And the culmination of this is that Jade, not Dirk or Rose, is the one to reach an understanding of her Ultimate Self, and realize that all parts of her, even the ones she hates and lets herself forget, make up the whole.
Act 1-4 Jade is a very silly girl who can’t focus on anything. Act 5 Jade excises this part of herself, and Act 6 Jade lets her duty take her to sadder and more isolating places. Re-reading Act 3, it’s frankly bizarre that the Jade whose first major on-screen act is to squeal like a piglet and fertilize some plants has to be told to try to loosen up.
And Jade playing with the dogs isn’t just a way for her to relax after a long day’s getting possessed. It’s the culmination of all the different Jades we’ve seen, into an Ultimate Jade who’s as capable of having fun as Act 3 Jade, but is able to get the job done like Act 5 Jade. And when Jade combines and uses all the aspects of herself…
There’s no rule she can’t break.
And in that sense, Jade’s story is the most satisfying arc in all of Homestuck, a better realization of the story’s core themes than Homestuck itself is, and while her getting possessed again in the epilogues is kind of a kick in the teeth, it makes her breaking possession so soon in Homestuck 2 sweeter. Jade’s been possessed a lot, and we had a whole arc about it. We’re done. She’s done, because she’s moved past it, and she’s going to solve problems her way, no matter what any rules are, no matter how much everyone is disdainful of her sleeping around, no matter how many authors or gods have a better idea for her.
I am Silver Tongue, I am an artist. I have many characters and you can check out my art in the art tag. I occasionally practice witchcraft though I don't do anything too complicated. I am girl 2 and don't know what else to put here.