Abiding by honor codes and behavioral codes gives you reputation with people who follow the same code which modifies their reaction to you.
Having a good reputation would be necessary to move in some circles, likewise honorable, shady or shadowed.
The same behavior may be admired by two factions but have opposite faction reputation effects.
Example: a knight who cuts their way through a battle to kill the opposing Lord might get -100 faction points with the other faction’s knights but gain +100 honor points with them at the same time.
An honorable enemy will be treated differently to a dishonorable one.