I mean from my point of view it should not be ban-able. You brought the plot, invested a lot of money into it and certainly decided you don't need it anymore or just need the money for something else. So why ban someone who want to give someone else the opportunity to acquire a plot? If SE wants to stop it they should implement a system, where people who want to get "rid" of their plot get a compensation to do so. Either 100% the current price back or at least somewhat of a compensation. As long as SE does not come up with such a system, people will continue to sell the plots they "rightfully" own.