Would it be morally fair of Nexon to ban buyers/sellers of NX? I think not.

But not throw you in jail too for a day? There's a thin line between acceptable and overbearing.

there were signs already telling you to not do the action. if they keep reminding you to not do it, and then you do it, going to jail for the day would be acceptable, as you had no decency to actually read the sign and actually listen to what it said.