That's not exactly what it says. It states that Archdukes are automatically granted a world as a personal preserve, but it doesn't stipulate what political role other nobles have on other worlds. The essay states that a noble is granted a fief, which is a parcel of land to rule. That's what a fief is in feudal system is.
Admittedly it doesn't say how the noble administers the land, but it's his.
I wonder how other players play their games with nobles.
There are pretty strong (50kg wrecking ball to the head kind of strong) hints in CT.
The Library Data A-M article "The Stars" makes it explicit that "
Interstellar government begins at the subsector level- on one world designated the subsector capital." It also states a subsector is ruled by a duke. "
This duke has a free hand in government, and is subject only to broad guidelines from his superiors. But at the same time, the duke owes fealty to the higher levels of government, ultimately to the Emperor himself.". (S8 p11)
It's also explicit that Nobles are appointed by the Emperor and the Archdukes... Heredity is not a guarantee. Local officials are not high nobles, either - T4 later makes it clear that new member worlds' initial nobles are often, but not always, the initial nobles.
That fiefs aren't an automatic is in S11 p.36. The fief is issued as a separate document, and is implied not to be a whole world (excepting Archdukes).
S11 page 35 makes it clear that most nobles don't get anything but the fancy title. The exceptions are those "associated with" various worlds and clusters. Note that these nobles aren't "goverment" - because government doesn't begin until the Subsector Duke. (per S8, p11)
In TTA, we see powerful nobles who are clearly too busy to be ruling their associated worlds... And lots of indications of surplus nobles who are down on their luck.
JTAS 14 gives us a strong glimpse into other related elements.
The Article High Justice gives us a lot of good info.
- "Mid Justice" is subsector level, and concerned with protecting worlds from exploitation.
- "High Justice" is sector and domain level. It's enforced by the IISS, IN, IM, IA. It's about trade and keeping the imperium whole.
- Subsector Dukes can have their own police and military forces.
- Subsector courts are hard to bribe. Sector and Domain courts are practically impossible to bribe
Further information can be extracted from the various adventures.
It's pretty clear that Barons, Marquis, and Counts are NOT governments unto themselves. They appear from CT and MT sources to be both agents of the subsector duke (by appointment of the Emperor), and a channel for local information and desires to become known to the subsector dukes.
Sup 4 gives us more information as well...
we can infer from the CGen rules that birth alone isn't enough to make one a high noble. You have to be in the right place at the right time. Promotion within the working nobles of the courts is extremely slow -
roughly 1/12 rate for the brightest sixth, and 1/36 rate for the rest... which, ignoring the 1/6 chance of increase in intelligence for each PDT roll, means that only about 1/4 of career nobles ever get promoted...
Actually, it's worse than that... because about 14% don't find a position in years 1-4... and 2% still haven't by year 8... and about 0.3% by year 12...
It's still a surprisingly large number.