Basically, is there anything illegal about landing at a private site that isn't an airstrip, and whilst doing so, flying within 500 feet of a person, vehicle or structure?
No.
But, practice approaches (intentional go arounds) are subject to the 500' rule.
MJ
Ps. In the case in your other thread, uninvited guests have not broken any rules of the air, so long as they land, and takeoff.