I think the author’s hypotheticals are off. In a world where blackmail is allowed, I think transparency would just be more normal, and secrets would be more rare. For example, people would be more open about cheating, sexual preferences, etc. I think in that world, along with blackmail, many taboo things would become more normalized.
I think that would be true in a culture made of Homo Economicus, but I think you're going to have a rough time of that plan with Homo Sapiens. Status matters, and there's going to be some way to judge that status, and there's going to be some delta between the society's understanding of your actions and their assessment of the resulting status and your actual actions, and some way to blackmail with that.
I mean, we already at least have subcultures that are fairly open about cheating and sexual preferences, but then those same cultures will nuke your social status into oblivion if you accidentally say the wrong racist word. (Let alone in a just a moment's poor judgment do it deliberately.) There's gonna be something.
But I would endorse the idea that there will be second-order effects, some of which may mitigate the problem. But I think that a lot of the people inclined to propose this wouldn't particularly enjoy them, either. For an example ripped from the headlines, as it becomes increasingly acceptable to nuke someone's political career for making a woman somewhat uncomfortable forty years ago (that's a deliberate satirical exaggeration, not a characterization of any real case), I've wondered if the people making that accusation are really thinking things through; do they really want to limit all public office only to people who were so socially clumsy and awkward when young that they never made a false move because they never made a move at all? I mean, hey, suddenly that would open up rather a lot of high power careers to me, sure, so I suppose I'm self-interestedly all for it in a sarcastic sense, but I'm not sure everyone's going to be interested in that being the criteria for serving in office or for that being the cost of leading a peaceful, unblackmailed life.
'There is a difference between “making a move” and “harassment”.'
Along with the fact that I suspect you are trying to refer to a specific incident, I'd point out that in a world where everything is subjective and in the eye of the beholder/victim, no, actually, there isn't. This is relevant in the context of discussion of "blackmail", if your definition of "make a move" happens to be their definition of "harassment". Even if "heavenlyblue" thinks it's the former, it's not going to help.
No, there is: if the victim told you it’s harassment, you immediately stop. You jail those who don’t stop after being asked to stop.
Legally speaking you don’t need to define the ways in which the law allows you to unconditionally communicate (verbally, physcally or non-verbally) with me. If I told you to stay back - then you should stay back and I don’t owe you an apology.
You’re trying to reduce everything to relativism. I think the real world is quite a bit more black and white in such cases. And we have jury for the cases that are gray areas.