Nobles have, per the IL7 article, plus the JTAS 24 Justice article, VERY little real power, except upon their fief.
They have no exemption from local laws.
They make no law outside their fief†.
They have no individual judicial power outside that which is part of their fief†.
They have income from their Fief, and may dispose of some parts via lease and/or (local) subinfeudation.
They have access to the subsector moot; voice in whichever, and vote in those where they have a fief. They can serve in certain high-office positions that non-nobles may not. On the other hand, when a subsector or sector duke decides a non-noble is the best man for the job, he can ask his archduke to elevate the guy...
They have LOTS of duties -
- To inform the subsector and sector moots of the needs of their fiefs' worlds.
- To inform their archduke and the Emperor of those worthy of elevation.
- To inform the subsector and sector dukes of threats that need "imperial attention"
- To administer their fief
- To govern the people of their fief - just, fair, and within Imperial law.
- To fulfill whichever offices they may hold in the subsector or sector governments.
- To advise the local world (and system) governments on how to interface with the Imperial Government.
- To encourage local and system government to obey imperial law (and report when they refuse)
- To be an example to the common man
- To coordinate between local agencies and their imperial counterparts.
- To maintain their Huscarles, if allowed, ready for and trained to Imperial Army, Marine, and/or Navy standards, as appropriate.
Lots of duties, little authority. And all under the ever annoying eye of the Press.
†Excepting those few who are also the local government of the world. There are a few. Including 7 worlds for one archduke that are direct subjects of the Archduke. (See Atlas)
Using that same logic an American Senator has very little power.
- They have no exemption from local laws (with the very minor exception that they cannot be detained when going to or from a congressional session).
- They individually make no law at all.
- They have no judicial power at all.
- They earn $175,000 per year (which is a nice salary but hardly what they could earn as corporate CEOs and the like).
- They have can vote in the senate.
- They can serve in certain senate positions. On the other hand, these positions give them no additional voting power.
And they have to do all of this under the eyes of the press while having to deal with re-election every 6 years.
Additionally, several of the responsibilities you list for a noble also include significant power, so rather than being a burden they are probably an asset.
- The ear of the archduke and the Emperor of those worthy of elevation (a nice carrot to offer to wealthy and/or influential commoners to convince them to do what you want).
- The ability to declare that something needs "imperial attention"
- Whatever additional powers they may hold in the subsector or sector governments.
- The power to advise the local world (and system) governments on how to interface with the Imperial Government (which is very significant, especially when combined with below).
- The power to report when local and system governments fail to obey imperial law.
- Influence between local agencies and their imperial counterparts.
- Permission to maintain their own armed forces in some occasions.
First off it depends on who ranks who on whether they feel like you do or not, if I rank them they are gonna suck it up to get what they want. Probably.
Not if you've succeeded in getting yourself ostracized. Seriously, if you're a noble who are you more likely to pay attention to, a Count who has pretty much isolated himself from the other nobles or a Baron who has firm control over a fairly substantial block of votes at the subsector moot?
Also, don't care if the fops don't dig me, Travellers will, I'm willing to get dirty.
But Travellers don't have any voice in the moot. It's great that they love you, but that does pretty much squat all for your power base.
Plus I come with nice toys and Travellers love toys.

Funny what they will do for a BattleDress, legal like with papers and everything. Hell if they do a good job I may even use real papers that don't fold up and disappear in two months after they leave the system. . .
Except your papers are only legal within your fief, remember? Of course if you were an
influential noble then even if those papers didn't carry legal weight outside your fief they might convince people to give the Travellers a pass. After all, while they can
legally refuse to acknowledge the papers they might prefer to accept them in the hopes of getting you to do them a favor in the future (something they are less likely to care about if you have isolated yourself).
In short, there is a very real difference in 'power as written' and 'power as exercised'. Yes, the 'power as written' for a noble is very limited, but that's all the more reason for networking with the other nobles. It's when you do that that you are able to substantially build up 'power as exercised'. Since your average subsector seems to have about 40 systems the subsector moot probably has between 100-200 nobles (depending on how many fiefs per system you think exist). 1 vote out of 150 for things affecting an entire subsector is a pretty powerful thing. It's not enough to pass whatever you want, but it's enough to make the average people who have no votes want to stay on your good side.
On the other hand that 1 vote you control will probably mean just about jack all to someone else who also has a vote, so don't count on any other nobles to give you very much in the way of respect for that vote. However, someone who makes friends, twists arms, and has a lot of people who owe him favors who can promise 10-20 votes on a key issue? That's a guy that even the subsector Duke starts to pay attention to (because he wants to get that guy on his side since he represents a good portion of the 51% of the votes in the subsector moot that the subsector Duke is going to want to be in control of).
Of course the only way to get control of those 10-20 votes is to get respect. You can pretty much forget about buying them outright. Sure, there are going to be some votes for sale but you'll be matching your wallet against 50 other nobles plus various plutocrats. Even if you can afford a couple of votes you'll go bankrupt long before you can afford a sustained coalition.
To that end a yacht can be a tool. It is something designed to elicit respect from other nobles (and plutocrats). The small fraction it may earn you won't be enough to win their support but it might help you get a foot in the door.
On the other hand if you show up in a ship that says 'I clearly have no idea how to play the game' then why should they give you any respect or support at all? Your first impression to them is that you will never be anything more than one of those people on the fringe. Maybe you will build up a tiny coalition of a handful of votes from other fringe members if you work really hard but that just means you'll be the person that the bigger powers lean on (and I don't mean that in a positive way) when they want to bolster their numbers.
Does this mean every noble sailing around in a yacht is a Machiavellian schemer trying to build his power base? No. Odds are pretty good that he's one of those supporting guys in that block of 10-20 votes. If the subsector moot has 100 votes you can only have 5-10 guys controlling 10-20 votes, so clearly not every noble sailing a yacht is one of them. On the other hand, he is much more likely to be one of those guys then the guy sailing around in the converted merchant ship (not saying that guy in the converted merchant ship
couldn't be one of those guys. Just saying that the odds go way down).
The fact is that a man who wants to act virtuously in every way necessarily comes to grief among so many who are not virtuous.
-Niccolo Machiavelli