It's no different than Star Wars; sector (star system) governors are called Moffs, with Grand Moff Tarkin being equivalent to a Duke, answerable to the Emperor only. Even Vader couldn't fuck with Tarkin because he outranked him.
I feel like it should also be stated, that a nobility based system does have some merits. One of the key merits is that a ranked person can manage a property with less oversight from a central organization. This is useful for where communication is slow to travel or the scale is too large for a central authority to manage well. Now, there are a lot more demerits, but I think it can have a use in space, considering even in the comic's universe it can take weeks to travel just moderate distances. Lots of area to manage, which is why pirates are so common (hard to patrol it all).
Without noble families, they'd need a system of states run by chosen individuals (apointed or voted in), under a united authority, so temporary nobles. Merits / Demerits here too.
All that aside, unless there is some cultural revolution, like what happened in Star Trek, I don't think cultures' and society's will change too much, given even thousands of years (without severe events - mass destruction level stuff) or lots of pain (read as "Justice" - political movements such as voting rights or labor unions). I've looked over how much "power" individuals have in their life, and it can be tied to economic influence. There are more ways, but money (more like wealth though) is key. Where ever money influences those with political power, those without money will have less and will subsequently have what they have bleed away from them.
So, those "nobles" with all sorts of power will strive for more. Be it for some idea of justice or simply greed. There is nothing "Fair" about dealing with uneven power dynamics (such as a boss at a work place, or parent to child), since no one wants to lose something (what is gained can range from finances to pride, but something at the very least). If those with money at best break even, then it follows that some will eventually not break even (because not everyone is a philanthropist) and that will slowly erode those with less power to a state with even less.
Could give dozens of examples off the top of my head in all sorts of ways, but it will forever stand that rules and laws are made for those with power. It is their shield and their weapon.
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Anyways, what I was trying to get at, was that a nobility system being created makes sense as an end point, even without being in space. The pirates and citizens will need a "let them eat cake" moment before anything will really change, and how the pirates are characterized in the story, that isn't going to happen.
Didn't mean for it to be this long, but needed to complete the shell of the point to get an understanding of how nobles could be in space.