Ahoy all,
Here is a small index of all recent implementations that now constitute a significant improvement in how every player's relationship with other nations, is defined in the game.
First of all, we now have Rightful Rulers. As long as someone is at least 3 updates on the throne, in the last 5 days, he is named as such.
The Righful King can now list target fellow countrymen as Enemies of the Crown.
Attacking an enemy of the Crown, will not generate any hostility penalties with the listing nation or your nation. Instead, it will award you Honor with the listing nation.
Honor is the opposite of Hostility. Right now, the only usage for Honor is to negate Hostility.
All the above are fully implemented into the game as we speak.