Kokuto:
As I've said before, I hate to use labels like stalker or toxic abuser, because they lack context. They are simplifications of actions that strip them of nuance and that ignore the complexity of the characters. That said, Jing definitely gave off stalker and manipulator vibes to me, from the very beginning. When XY told him he was healed and get lost, and he refused and pleaded pitiful to stay, the hair on the back of my neck went up. Him saying he can't help himself when he follows her or does things to sway her, doesn't help either.
But, like I said, there's context. I think Tong Hua meant these to be flaws, not character assassinations.
I don't want to do all the digging that would be necessary to find the original post, but I remember a YaoJing posting a long time ago about how XY and TSJ's traumas and insecurities are highly compatible. They aren't two healthy and emotionally well adjusted people who can have a healthy relationship, but they have somehow found a person who can at least give them what they feel they need.
In TSJ's case, TSH's torture was designed to make him feel dehumanized and worthless. By not only healing him with great care, but actually clearly finding him physically attractive and blushing over his body, XY makes TSJ feel like a man again. He ends up re-building his sense of humanity and self-worth, but it's anchored to XY. What other people think doesn't matter. Only what she thinks matters. If she's dead, his life is worthless again. If she is no longer willing to have a relationship with him and treats him as a stranger, his health is affected so deeply that his life is endangered.
In XY's case, she felt abandoned over and over again by the people who were supposed to love her. In most cases, they either abandoned her for her own good or for the good of the world. So she wants to find a person who is not capable of letting her go. Not even for those types of understandable reasons. TSJ is clingy and (with some notable caveats that are to his credit I think) not capable of letting XY go. She outright says she likes that, because it makes her feel secure. And when she constantly tests the endurance of his devotion, he's happy to prove himself over and over again. He does end up abandoning her twice. Once to marry another woman and once when he's murdered. But he definitely wasn't happy in both cases, and in both cases it was only temporary.
TSJ constantly following and watching XY is part of that dynamic. In context, it's not a fatal character flaw. Even if it is annoying for the readers / viewers.