Probably because OP is not seeking legal action in Hacker News Court, but in a real court where broadcasting details of such information is not a good idea.
What's outlined in the article doesn't meet the burden of proof. There was a conflict and OP solipsistically experienced it as a big deal. Meanwhile, there's plenty of oppression and destitution in the world, but let's all focus on some low-level drama because it's more entertaining.
It may be low-level drama to you, but clearly the author felt threatened by the couple. The spam messages, the threats to release personal information, etc. I would have no qualms with seeking legal action.
Personally I'd feel really concerned if someone upset at a conference ... contacted a personal acquaintance who is involved in it all like a girl friend.
To me that would indicate some serious "boundaries issues."
Much closer to high school drama than illegality. OP will never obtain any judgment. I didn't think the HN community would so easily succumb to mob mentality due to a compelling narrative about a non-problem but I guess this is the Internet.
In cases where someone feels harassed "judgment" isn't necessarily even the point.
Legal action is taken, you get a lawyer, they get a lawyer... often their lawyer tells them not to contact you or people you know anymore (because that is what a good lawyer will do) and it is effectively resolved. For some people that may be enough / the entire goal and it can cost as little as everyone talking to a lawyer once.