I'm guessing it's a way to force Signamancy you project the appeareance of being rich/noble, then other characters react to those traits either positevely or negatively.
I wonder whether signamancy as clothing does more than just change the way other people view you. It might actually be a "clothes make the man" kind of situation where dressing differently actually buffs some of your skills. Natural signamancy changes the way units look, so that their appearance matches their role. Maybe it works both ways, so that by changing your appearance you can change your role. If you dress in badass looking armor and facepaint maybe it makes you a slightly better fighter. And if you dress in costly gold jewelry, maybe it makes you better at diplomatic matters, or at negotiating financial deals.
What if it's the opposite? What if dressing improperly
for a role or a task gives you a signamancy circumstance penalty to perform that role/task? Like going into battle wearing court garb and fancy jewelry makes you worse at swinging your sword, unless you're specifically doing it to dance-fight or rock out?