I have just re-read The Algebraist & wow! Yes I do love it, though it does get hard going in the middle.
Ok so first - I think the Mercatoria could represent, or be influenced by the 'East India' companies (clue is in the name), which were a deniable, gloves off instrument (weapon?) of Colonialism; ie if one of these companies had taken over an imperial structure.
At the end, when Taak is talking to the Gardiner, HG, he says "I am already a citizen of the Galaxy... " which (for me) inverts the whole novel perspective, one of those Banksian flips? You see, up until this point, we have been seeing the whole Galaxy from the Mercatorial perspective, within their sphere and their propaganda.
The Starveling breakaway cult is still coming out of the Mercatoria (almost a meta charcature of it), which uses a pan species, pan epistomological cult ('The Truth') as a tool of control (ie the conv. with the Colonel re Taak's belief in the Truth & whether he is holding it in the forefront of his thoughts).
The Truth is a self separation ideology that causes the adherents to doubt their material world & even their own being, which is similar to how the concept of an 'Afterlife' can function to make people disregard their own safety, growth or natural desire for justice/emancipation.
Also the 'must be thinking about all the time' & how superiors examine juniors reminds me of the Catholic 'confession/god is always watching' inculcation, which pre-possesses the very self: sheer mind control through self thought policing (I am not singling out the Roman cult, I grew up in 80s Catholic Ireland, this was drummed into us in childhood, in 'National' schools, best example that I have).
It is another example of the Mercatorial authoritarianism; a subtle, but actually quite frightening example of how much control they have over the thoughts and worldview of those under the influence.
This led me to wonder how much the worldview of the Mercatorial Ulubists is gaslit and distorted.
The Beyonders are initially presented as bandits, like fringe rebels that sort of raid occasionally, at random; but later on, we learn that they actually only hit military targets; that when they do this, they are hitting back; that the Mercatoria are accused by them of killing many civilians in Beyonder habitats (implying much higher levels of social & technical & civilsational organisation than one would expect of bandits or rebel enclaves).
Also, as the novel progresses, we see many different Beyonder species mentioned & when their perspectives appear, towards the end, as the starvelings & lechiferous invade & retreat, they appear to have pretty good tech & ships (ie the microsat undetected by the U Mercatoria).
I posit that the Mercatoria do not let their subjects know anything about the Beyonders, or their constant harrying of them. In fact, they call them "Beyonders" to stop their citizens even thinking that there are other cultures around, perhaps more egalitarian, easier to live in; as evinced by the fact that the best, most described examples of the Beyonders we get are 2 female characters (Although I suspect Aun is an AI).
When lechiferrous meets the Beyonder, he is annoyed that she is a woman, but unable to demean her, or torture her for information & kicks, which implies that they have more power and organisation than the initial presentation. She has a high rank in a military structure, which could show a more egalitarian structure than the Mercatoria
Aun: she is a honeypot aimed at the kind of egotistical, vain man the Mercatoria produces, whether Lechiferrous or Sal
She is like an SC operative in the field; there is even a moment where she freezes for a minute, with Sal, then catches up (ya know, the nueral lace download thing), which could imply greater tech.
Well, we don't know that the Beyonders work with AI, we just know that the Mercatoria hunts AI, which could also be a pretext to try to invade, or destroy a threat to their power / brainwashing.
I am not saying that the Beyonders are the Culture, or even proto Culture, but that they are perhaps similar, but more loosely connected?
It all goes back to the phrase "I am already a citizen of the Galaxy... ", which I took literally rather than poetically; ie the Mercatoria is perhaps a small, tight authoritarian group which came out of a military coup during one of the disruptions; that there is a bigger Galactic culture which has retained more knowledge & tech, (which disables the wormholes to prevent the Mercatoria from spreading & sends in SC like operatives, disables only military sites, which also hints at a more egalitarian, human rights based society).
Perhaps, a crude analogy - the priest in Eric the Viking wanders an empty plain, while the Vikings are in Valhalla.
I also think that some Dwellers do cooperate or meddle, or get involved to a greater degree with Quick, but perhaps not so much with the Mercatoria.
I mean, you can't really trust Dwellers, but that is also a matter of you bringing your own circumscribed thinking and worldview bias into conversation with what remains a very very ancient and alien species.
I mean, they could be playing a game with the whole Mercatoria & Beyonder civilisation all along, with Taak's quest, for the lulz, or as an experiment, all the while enjoying the joke of it being in his pocket, right under their noses all along.
After all, eternity is long & one needs diversions.
Overall, I think a huge theme in this novel is that of perspectives & how certain perspectives constrict or even change the world that we think we are seeing, and even the knowledge that is right under our noses the whole time, only our epistomological walled garden prevents us from seeing it (ie the Equation =0,that the Beyonders are not just annoying bandit rebels, that AI exists & the Dwellers don't care etc)
Also, the bit with the Voeht ship mind describing itself as a complicated autocorrect, not sentient - well, I saw that as a dig at our (real world) 'AI' - our genAI slopification LLMs
Anyway, some may disagree, but these are observations that I had reading The Algebraist which I haven't noticed anyone else discuss