So, imagine two situations.
1) A pretty girl is walking down the street and you begin whistling and leering at her, shouting obscenities and loudly describing all the ways you will pleasure her. This being an ancap society, the street where the girl is going is owned by one guy, and you're at a construction site owned by someone else. Aforementioned girl claims she was psychologically harmed by your derogatory remarks, but there was, of course, no coercion involved.
2) Same situation, only that this time, instead of screaming, you just walk up to the girl and slap her. Obviously you've harmed her but there was actually no coercion involved (was there?) because there was no threat.
So, what applies here. I assume in situation number two she can have her PDA drag you to court and charge you whith assault, because you harmed her, no question about it. But what happens on situation number one? If you really harmed her, she can also drag you to court, but there was no coercion involved, they were only remarks (derogatory and disgusting, but remarks nonetheless).
I guess my question is, was there really harm involved in number one? If not, why not? Because as I understand it (from reading Block) there is no harm because there is no coercion in screaming, but then again, what about number two? There is also no coertion (only random street-slapping).
"This being an ancap society, the street where the girl is going is owned by one guy"
Generally not going to be the case... for that particular street - one organisation perhaps with many shareholders, but management and the person who has direct say over the running of the organisation, yes ok.
"and you're at a construction site owned by someone else. Aforementioned girl claims she was psychologically harmed by your derogatory remarks, but there was, of course, no coercion involved."
Someone could just as easily taken it from a different perspective and as such, a compliment. Does the construction site you are working at [and thus have a contract with] have stated rules of workplace behaviour? Those actions taken would reflect poorly on the company, no?
"2) Same situation, only that this time, instead of screaming, you just walk up to the girl and slap her. Obviously you've harmed her but there was actually no coercion involved (was there?) because there was no threat."
It is the initiation of physical aggression.
Anyway - I'd recommend: http://libertarianpapers.org/2010/13-borer-risking-aggression/ to make things clearer.
Or to get right to the point - Rothbard; Air, Property Rights and Pollution - Physical Invasion talks about the harm principle.