Since I didn't see the original post and don't know the details, I can't comment about what happened there, but thought I'd share what my dad did. My property line with my neighbor does not have a fence, it's just a trail that I created on my side of the line, that is fairly close to where I think the line is, but neither me or my neighbor has put any effort into figuring it out exactly by running a line from the surveyors corner markings.
We where having a lot of fires one year, so I asked my dad to drag the dozer blade along the roads and trails to give us a bit of a fire break if anything headed our way. He got confused and for some reason that he can't explain, he drove the dozer off into my neighbors land and started pushing over trees and clearing a fire break through his land. He took out dozens of trees of all sorts of species, from good straight pines, to some nice oaks. I think he just got into the moment and thought he was doing what I had asked him to do, and got confused with scraping the grass off of the road and opening up a fire break.
Once I saw what he had done, we both went over to the neighbors house and told him what had happened and apologized. He went with us back to where dad had taken out his trees and saw how ridiculous it was for Dad to have gone off into that direction. He's a good guy and he just laughed it off. He asked us to clean it up and he wold just consider it a new pasture area in the future. Since then, it's grown back in pretty thick and he has never done anything to maintain it as a pasture area, it's all back to jungle again.
Then last year, he had a crew on his land mulching and clearing parts of his land to remove the underbrush and widen up some of his trails. They got off course not too far from where Dad had taken out those trees, and they cleared about an acre of my land. It was a beautiful job, but not what I was planning on doing in that area as I liked having the underbrush there as a visual block to seeing past there. He came and told me about it, and we just laughed it off.
Sometimes, its not intentional and once done, you can't undo it, so it's really no big deal.
Eddie