High SOC on it's own does not a noble make, the noble carers do.
It's fairly easy to separate them so the SOC bonus is reputation or charm or social standing where as the title comes from terms in the career. You can have a charter whit high SOC who is well know (or infamous) while being guttter born and common as dirt and a noble of the highest rank who is widely known as utter scum (Harkonen).
You can use the title as a forced DM where as the SOC is a willing one, people love to help out the Tri D star or that woman who single handledly saved a whole liner full of war orphans and is known across the sector, where as everyone treats the scumbag as a noble because he is powerful enough to have you dealt with if you don't.
The DM applies all the time under normal circumstances but can be removed at times, like when Harkonen is in disguise or on a world where he would be killed if identified and so has to use his natural SOC instead. Flip side being that in noble circles away from the media the lords and dukes care less about a boat load of orphans and the jumper up commoner with delusions of being one of them just because the arch duke grabbed some free publicity and made her a knight.
Or to put it another way, Harkonen using his ducal status, +4, being his less than charming self, -1
Heroic type, ex navy, SOC +3 with extra +1 for reputation when playing the media angle at home, or +0 when trying to impress the hereditary lords becasue she's just a knight and from a commoner family.
Note this works when you don't use the cute and fluffy Imperium where nobles are all good and kindly folk who serve loyally and play a more realistic and gritty game where the nobles are just like anyone else only richer, more powerful and a social class to themselves.
