All the concern Jackie and the other heroes have for Jade, even after her Face–Heel Turn, and their desire to cure her is VERY heartwarming.
All the Jackie Chan Adventures fans who wanted to see more of Jade's Superpowered Evil Side from canon are decidedly happy at this fic. Also, it's part of a group of stories by various authors called Project: Dark Jade, all featuring a dark form of Jade.
You can find the description of the project on his Fanfiction.Net page (the link is on the main TV Tropes page for the fic).
Everyone who secretly roots for the Enforcers should be happy to hear that they are finally getting paid for their efforts.
This has inspired great loyalty towards Jade in them, and during Valmont's attempted coup and Ikazuki's more successful one, Ratso and Finn, respectively, helped her stop it and regain control (again, Finn was more successful).
This loyalty extends so far that even after Jade fires them and they're soon after arrested, they still refuse to rat on her.
When Jade has the Dog Talisman destroyed, it's before she even KNOWS about the masks, and there seems to be no ulterior motive other than making Scruffy immortal.
Left and Right's loyalty towards Jade is EXTREME, so much so that it plays the ol' heartstrings.
In particular, there's their concern for her during and after her encounter with Lung, and the scene in Interlude 5 when Left comforts her after a nightmare induced by said encounter.
While Left has more moments of being close to Jade, Right gets one when he comforts her after her confrontation with her father, specifically the reveal that she was conceived accidentally and almost aborted.
And there's Left going Papa Wolf and telling Shen not only how unworthy he was to be Jade's father, but also threatening to kill him if he doesn't do what Jade said and leave town.
In "Sins of the Father", it's revealed that Father looks exactly like Jackie, meaning that before her Face–Heel Turn, she viewed him as more of a father than her own biological dad.
Jade playing with the Mini-Khan.
Jackie and El Toro reaffirming their desire to save Jade.
Jade and Hebi pigging out on sushi, then sitting on the couch together.
The fact that despite firing the Enforcers, said Enforcers still refuse to reveal any information on Jade's whereabouts since she was the best boss they ever had.
Jackie remembering the times Jade would perform a Stealth Hi/Bye on him, and states he misses her doing that.
Even when it looks like Jade is going to kill him, Tohru just continues trying to get through to his friend. And her homunculus sacrificing itself to save him seems to indicate it worked on some level.
Jackie saying that he's disregarding Karasu's warnings about the future, because even if they're true, he knows that history can be changed, and therefore he and the others will never give up on saving Jade.