Keep in mind, none of these answers are set in stone. They're just "this is what we are thinking right now."
Q. What are the cultural values of this society?
22nd century (CE) society, like when capsulerp takes place, I imagine as having been deeply shocked by the extent to which climate change happened. A lot of species and societies were destroyed altogether, and while the people in charge today are the sorts that don't mind we like to think maybe other people would have been affected. That there was sort of a "my god, what have we done" moment for everyone, in this case catalyzed by dialogue with the cetaceans.
There's plenty of Suul'ka to go around, still, and you can see that in the numerous megacorps they have, much like today. Most of them are what we would call "B Corporations," though, and have to at least pretend to have a social welfare component to their mission. Wealth for its own sake is no longer a socially acceptable goal; if anyone amassed the kind of cash hoard that Apple today has, there would be calls for them to either invest it in the people most adversely affected by their operations or relinquish it.
Q. You mentioned diversity of minds in the right to uniqueness section. How is that constructed and why do people ascribe value to it?
That's probably the biggest cultural value of the 50th century CE, the time when Analogue and Hate Plus take place. There are a lot of reasons for it, but the biggest one I can think of right now is that perhaps the two rarest, most valuable things in the universe are as follows:
Complex organic molecules, like proteins,
Diversity of minds is seen as an inherent good, sort of like biodiversity at an ecology seminar. Every creature has the right to exist, simply because it exists, and also because by letting it be it creates more independent thought.
This is going to sound creepy, but you know the way the Borg introduce themselves? "We will add your biological and technological distinctiveness to our own?" 50th century society is like that, rabidly seeking out things like lost colonies and the rare exomorphs. Except that instead of wiring it into a hive mind, they want you to stay distinctive, since distinctiveness is rare and valuable.
Example: Now that the Mugunghwa has been discovered, pretty much everyone interested in the fate and history of ancient generation ships is going to be reading the same logs that the Investigator did, and discussing / roleplaying / fanficcing the parts that interested them.
This is exactly as awesome, and exactly as disturbing, as it sounds.
Q. Why is there so much emphasis on people's origins when people are seen as a current process? Do essentialists object to any radical change in individuals?
First, "essentialists" aren't a group per se, so much as that everyone has a certain degree of essentialist thought in them. There's an inherent conflict between "uniqueness is valuable" and "people have the right to change who they are," and this doublethink leads to blind spots and hidden biases.
Example: *Mute, the lost starship Mugunghwa's security AI, is an extremely valuable consciousness, simply because of her experience in that isolated society. She may well have fanmail, stalkers, and even cosplayers somewhere out in Star Union space. So how do they all react if she makes a dramatic change to who she is, or adjusts her values and ideals based on contact with modern society?
Q. How is death seen? Is it more or less feared? How often do people die unwillingly? Do people avoid thinking about death?
That depends. Is it my death we're talking about here? In that case it's terrible, it's like a star going out. It's something that we can prevent, by making backups. Thank goodness for modern technology!
Is it the death of a space cow somewhere on a distant planet? Well, that's just how, like, nature works, man. Your body feeds predators, and nourishes the soil for the next generation of space cows. It's the Circle of Life; it's so beautiful :')
Q. What does family structure look like?
Not anything like what *Mute wants it to look like!
"But that's ... ugh. I mean, what can ... I don't ... how does that even work?" *Mute finally asked. "Does one of us pretend to be the husband, or something?"
"It is normal for women to marry," I told her, my knees shaking.
"Not when they marry each other!"
"Yes, it is. It is completely normal on Earth. It's a tradition," I told her, hoping that'd make it okay.
"So that'd make us ... what? Wife and ... wife?" *Mute said it like it was the strangest thing she'd ever heard of.
Q. What is taboo?
Violating people's consent, first and foremost. There's just a wide variety of opinions as to what constitutes "people," and what constitutes "consent" when it comes to non-people. Both of which would seem liberal compared to today, but still lead to disturbing edge cases that say more about the person who has that belief than anything else.
Also, and related: diminishing the amount of uniqueness in the universe.
I'm going to briefly touch on three concrete taboos that are related to these two: Bestiality, cultural appropriation, and self-diagnosis.
Bestiality is theoretically taboo because non-sapient creatures aren't considered able to give informed consent. In practice, though, it is largely driven by "ick factor," or the nausea that people feel when they think about cross-species sex acts. Because of that, you will often see the bestiality taboo invoked to declare consensual sex acts off-limits, such as between an AI and an uplifted animal ... or even, sometimes, between an AI and a human.
Cultural appropriation is theoretically taboo because it diminishes uniqueness, by letting you and your interpretations of others' society talk over their own. It's a taboo that partly dates back to people in Suul'ka settler states becoming self-aware about genocide. In practice, though, it is sometimes itself driven by xenophobia, as the idea of someone from "our" society taking on "their" society's characteristics threatens unspoken assumptions about cultural supremacy.
(Like, say, the idea that we in the Star Union are so progressive and enlightened that we preserve and appreciate other cultures! "Not killing people" is a unique thing that makes us special! Yay us!)
So like, people are usually okay with the aforementioned fanfic and cosplay and stuff. But as soon as it seems like you're serious about taking on another cultural identity, people are like "oh my god she's not joking." Then your social status shifts to somewhere between "anime geek" and "furry lifestyler."
Dysphoria is real. But what that means, to a lot of people, is that it can be measured and quantified, like in the "brain scans for transgender people" they talk about today.
So what if your brain scan comes back negative?
In that case, you may be experiencing mental distress. But it can't be dysphoria, because they know what that physically looks like and this isn't it.
Over the last few thousand years, attitudes regarding this have shifted to be more accepting of the fact that diagnostic instruments are not perfect. But while people will accept your feelings as valid, they sometimes jump to the conclusion that you are having them because you're mentally ill, not because you are legit disabled or dysphoric.