Originally posted by Aramis:
Most especially the role of Imperial Nobles. Are they virtual representation? Are they Governors-general, able to override local laws? Are they consuls for the imperium to the local world? How much pull does the subsector and sector moot have, and how much does the noble in said moot have?
All these decisions about nobles strongly shape the role of the 3I as a whole.
This is correct.
Generally speaking, my answer is that the nobility are predominantly drawn from local elites. They rule the worlds, and the more powerful ones rule more than one world. And others control the megacorporations, the fleets, the armies and the bureaucray. And the major churches, and...
The idea is that you buy their loyalty by giving them fancy hats to wear, and giving them a stake in the status quo.
If they get out of line, you stomp them, of course. But that only works as long as only some of them rebel. If more than one Domain was to rebel, the Imperial government would have to strain to suppress them. Even a single sector rebellion can end up taking decades to suppress, like the Ilelish Revolt.
Incidentally, if the Imperial government wasn't nervous about other sectors and domains joining that revolt, they probably weren't paying attention. That could well have been a reason why they played their hand so carefully with Ilelish.
Back to the main point: how much clout does the individual noble have? That depends. If they are hereditary President of the Democratic Republic of Bigworld, lots. If they are Mayor of Southern Boondocks City, not lots. If, however, they are also the favourite nephew of the subsector duchess, the Mayor may well have comparable levels of unofficial clout.
I was, of course, referring to their local titles just then. The Hereditary President is probably an Imperial Marquis, or even a Count, and the Mayor may only be an Imperial Knight.
YMMV, IMTU<>YTU, etc.