Apart from going around being obvious about one's status, and expecting deference because of it, SOC to me would indicate a certain level of upbringing. That upbringing would have a direct impact on general mannerisms. It might have some indirect effect upon charisma, but is more nurture than nature, of which charisma would reflect both. It can work in a PCs favor in some situations, and against them in others. Is the PC dealing with Duke Norris or are they carousing in a seedy downport bar? In the later, they may not want to project "affected" mannerisms. This sort of thing I would leave to role playing, but it could make a difference, mechanically, in certain situations. Rolling for NPC reactions and such
I'd say it's generally desirable to have a high SOC. As Spock said, "It's easier for a civilized man to behave as a barbarian, than it is for a barbarian to behave as a civilized man."