Maybe we should think about how we act online if we feel that there is a significant risk of being accused of cyberharassment, even if such conduct should not be illegal (and I suspect we also disagree on where the line ought to be drawn here).
In the context of criminal behavior I'd expect harassment to be a campaign of intentionally bothering someone and invading their space. I'd assume someone like Lin might be guilty of criminal harassment if he waited outside this girl's house and lewdly propositioned her every day, bothered her at work, etc.
I think we should have a higher bar for what constitutes cyberharassment because it's so much less invasive and threatening than physical harassment and so much easier to ignore. It's also possible that it's easier to inadvertently participate in cyberharassment when you can't see how the other person is reacting to you or feel how inappropriate the behavior is.
What Lin did in this case is far beyond any of what I described above. I think of his behavior as transcending what I'd describe as cyberharassment - in my earlier comment I called it psychological torture and I think that's far more apt than cyberharassment which seems too milquetoast a phrase for what happened here.
As for why my intuition went that way, I suspect it's because, from the title, I felt like Lin was wronged by the VPN company which misled him, I generally distrust the FBI, deanonymizing VPN traffic seems troubling to me, "cyberharassment" sounds more like being mean to people online than the things Lin did and I don't think sending rude words to people should be criminal, and I suppose that I personally am more likely to be (falsely) accused of cyberharassment than I am to be victimized by it which probably results in implicitly identifying more with the attacker than the victim.