OK, let me put it in legal terms for you.
If you make serious allegations about someone which are not true and which risk causing them reputational damage, this is defamation.
You can defend yourself against legal action for defamation by proving that what you have said about that person is true.
In this thread, you have made potentially defamatory remarks about JK Rowling, accusing her of transphobia and hatred and inciting violence against trans people.
From a legal point of view, if she saw your comments and decided to take legal action against you, you would need to provide evidence that what you said about her is true. If you could not, you would be guilty of defamation and you could be ordered to pay her compensation.
In reality, you're just a tiny fish in a big, scummy pond with thousands of other fish who are also defaming her. She's not going to get her lawyers to write to a little fish like you.
But in theory, if she did see your posts and felt minded to do something about it, if you weren't able to back up your claims about her, you could be in deep shit.