Credit to JoseP and a few other bright sparks in the discord for tracking every (at least, named) appearance of the twins and direct-mentions. I then wrote this answer document. I think the straw that broke the camel's back for people figuring out that 'something was up' was when one of them said: 'goddess' during the sleepover.

Stuff of Note about the Twins (Answers)

Chapter 14:
Hex and Binary appear with Radio, as they're part of the Radio club.
Heard of Emperor via mother, who said that someone at the hospital says that Emperor helps run the state's resistance.

Chapter 16:
Referred to as Hex and Binary for the first time, their mom buys a bomb.
Elias asks the mom to give the numbers of disgruntled people to her daughters (Hex and Binary).

Chapter 18:
Shil'vati interference making it difficult to contact Hex and Binary after their mom died.
Supposedly their motivation now is to avenge their mother and father.
In their minds the "...[Shil'vati] took our father from us. Then they took our mother. We'll... we'll make them pay."
Focus on the fact that the Shil'vati did not give their mother the chance to surrender.
They mention they're Phreaks.

Chapter 19:
According to Elias, "the Twins aren't exactly subtle in their loathing for the Shil'vati."
According to Radio, they're receiving "Mandatory Trauma Counseling."
According to Radio, "if the system feels it ain't right they're doing okay, seems the system can't accept that some people just don't take hits the same way."

Chapter 27:
Sentries are Binary and Hex.
Prisoner does not speak the language.
Hex was trusted to continue the interrogation to improve her Shil.

Chapter 28:
Radio is asked for contact with the Twins.

Chapter 34:
Mask reveal, complain about name "camp death".

Chapter 37:
The twins are the final stragglers before their first big operation takes place.

Chapter 38:
Binary was handed an omni-pad, along with papers with orders.
They attacked the cruise ship.

Chapter 39:
Binary confirmed to kill a Shil'vati.
They both magdumped the ship, along with others beneath them.
Binary initiating, they both decide to take the cannon with them.
Hex raises her rifle to rob the crew once more.


Chapter 43:
The twins see the Emperor's face and real voice for the first time.
Shil'vati tech was taken and stored in a discreet location to see if they're tracked.
Radio and the twins were excited at the prospect of locking up Shil'vati armor remotely.
The twins are in a foster home: Radio says "Sorry, unless your foster's home got a rig like mine..." to the twins.
Binary says "but what if something happened" after learning they were bait (though in general they did not seem too upset).


Chapter 46:
The twins have the suspicion that the Shil'vati "disappear" prisoners.
The twins have the assumption that they could buy a spaceship with tens of millions of dollars, even though it would cost way more than that.
They seem excited at the possibility of ransoming all the prisoners and getting a fleet, armor, and rifles.
They get rebuffed by the Emperor, who gives them a quick lesson in economics and some street smarts.
Dismayed at this, Binary then gives the recommendation to execute all the prisoners.
After the Emperor's speech on long-term Shil'vati slaughter, she suggests the disbanding of the security forces.

Chapter 47:
Binary mentions that they "struggle with the noble dialect", meaning that they know some, but aren't good enough yet to interrogate.
The twins figured they'd interview the marines (except Myrrah) in Trade Shil.
Interestingly, Hex says "what about one of the sisters?" when referring to herself and her sister.
In that case, we can say one of them was volunteered to watch the injured noble.
Instead of nursing, Binary is giving the honor of beating the hostile prisoner, as well as cuffing her to a pole.
Binary beats the prisoner and only stops after Hex pulls her back.

Chapter 50:
Hex executes a prisoner.
Although they try to object, they accept their punishment (though with protest and practically begging to not be handed over to Miskatonic).

Chapter 58:
While working for Miskatonic, Hex feels slightly disturbed by the screams.
She receives the advice "You should never let your feelings get in the way of doing what must be done."
Hex worries about having fallen out of favor with the Emperor, and says "I don't want him to be unhappy with me."
Head of Miskatonic (possibly Elias' dad) says Hex would get along well with her daughter.
It's admitted here that both Binary and Hex have a crush on the Emperor.
When the head of Miskatonic lightly teases, Hex has to consciously resist the urge to punch him.
Receives the advice to "become the thing he wants" and that "nothing lasts forever."
Hex receives the anti-grav harness from Siri, and she knows that she should drop it off at a different safehouse to test it.

Chapter 60:
Binary suggests giving the Medbot to Miskatonic in exchange for Hex.

Chapter 62:
Hex relayed her internship at Miskatonic.

Chapter 65:
When Senator Bouchard is first found, Hex drags him in.
She is also the one to suggest to bring a Doctor from Miskatonic to help figure out what's wrong with him.
After Maise tells the Emperor to join her in the medical examination of Bouchard, Hex just stays starting at her through her Jason Voorhees mask.
During this, Binary is moving the doc bot.
Once Hex realizes that Bouchard has no filter, she says "We can't let him leave her alive" and "Seems a waste to check him out, rather than let you play Doctor with Maise."
After Elias explains that Maise is a professional, Hex balled up her fists.
After reassurance from Elias that he'll holler if anything goes wrong: "She narrowed her eyes a bit at the nurse, who simply gave a wave."
She continues to show lots of protectiveness of the Emperor.
With two knocks, Hex opens the door exceedinly quickly.
Elias' misinterpretation comes into play here, we only have his inferences rather than concrete things said.

Chapter 66:
Hex sobs in the Emperor's arms after almost being killed by Myrrah.
"Binary, how's your shil?" - "Better than yours, but not as good as Hex's"
Hex has better shil than Binary.
Hex is also intently staring at the door where the Emperor and Maise are going over the brain scan.
Binary helps Vaughn by translating his orders to Myrrah to slit Bouchard's throat.
Hex gets told to "stop staring at her wannabe boyfriend" by Radio.
Hex commands Myrrah to slit Bouchard's throat with more intensity, and adds "like they had her father. Embrace [Myrrah's] true nature as a monster".

Chapter 84:
Elias while contemplating being taken away from his family, mentions "A spot in an orphanage, and that I got put with Binary and Hex?"
First no-show from the twins, explained by Elias as "brushes with death have a way of draining you". Possible adoption? [Yes]

Chapter 106:
We finally see them back at camp death.
Hex is still generally protective of the Emperor, with a short temper (directed at Gray Mask this chapter).
Hex suggests praising Elias Sampson "to get the Shil to disavow him."

Chapter 110:
Elias notes that the twin's attendance is "spotty", but that that their loyalties and capabilities are steadfast.

Chapter 111:
Verns says the twins are "all over" Elias.

Chapter 120:
Elias goes missing, stressing out the twins, particularly Hex.

Chapter 121:
Elias and Hex talk via code.

Chapter 138:
Elias responds to Hex

Chapter 139:
Despite Hex being very concerned for Elias, and being a tad obsessed, she hasn't written back to him by this point
[Adoptive mom has put them to bed. “No more Omni-Pad for the night, you’ll have trouble sleeping!”]

Chapter 141:
The twins are absent yet again
[There’s a reason for this- I think it was either studying, or more probably something to do with ‘family time,’ or the late hour. I again reference this in the new and upcoming chapter, where Mrs. Rakten references ‘even if she were a normal mom of a non-noble household, she wouldn’t let her daughter out unless for special circumstances.’ This references how the twins must’ve convinced their adoptive mom off-screen “But moooom there’s a boy! And one of them’s got a birthday! And we’ll be the only guests! We’ve GOT to go! Sleepovers are totally a big coming of age thing!”]

Chapter 145:
Hex and Binary show up again, and they were able to "piece something together" from the cell that made first contact.
Elias is relieved about not having to share about his whereabouts, simply because the twins refuse to share about why they were missing.
The twins complain about the alien's stupidly large tits.
Hex says all she knows is that she "doesn't like any of 'em."
The twins saw a different billboard, they didn't drive from the north, and this is of note to Elias, meaning it's not typical. [Yes. Driven from their new home near the military base- good catch!]

Chapter 146:
Hex is on edge during the meeting, and pulls a gun on the Nighkru when they touch Elias.
When Elias claims there is someone important to him, it's possible she thinks it's about her. [Yes]

Chapter 147:
She is distraught by Elias getting shot.

Chapter 150:
Binary says she heard a conversation between two Shil'vati nobles, which is where she learns of the idea that the Nighkru came to kidnap. [Yes. The Shil’vati do genuinely believe this to be true. Whatever the Nighrku’s genuine intentions, the Shil’vati regard it as true, which means Hex hears it and interprets it as truth. She also opposes Sam when he stands up for the Nighkru at the meeting, though that may’ve been axed?]
By this point Binary shows understanding of High Shil. [Yes. Learned from adoptive mom.]
Since Hex was known to be better at Shil than Binary, it's possible Hex is also knowledgeable of High Shil. [Correct.]
"People would die for you" - Hex

Chapter 151:
Hex is upset at being spoken for by Radio.
Elias mentions that from the speed they left, the twins must have been running late. [Late for pickup, staying out past Mom o’clock curfew]
Binary says "Spreadsheets hold the world's secrets."
Binary also recommends dyeing the fountain water - a non lethal option surprisingly. [She’s softening on the shil’vati]
She also says the Shil aren't too keen on sharing their tech. [True, which is meant to then run up against them having a personal Shil’vati datanet-connected omni-pad, big clue]

Chapter 157:
Hex was afraid that their efforts might be insignificant in the grand scheme of things. [She’s seen the span of the galaxy, and is starting to gain perspective, and laments the loss of her biological mother and father.]
Hex and Binary tacitly admit to already knowing that the Shil are lying about the situation on Earth (this is egged on by the Emperor though). [Correct. They know the reality of the situation, even better than their adoptive mother.]
The twins information dumps about Ministriva, how she's actually a major governess. [Correct. They would’ve heard about it from their adoptive mother, or on the Shil’vati DataNet.]

Chapter 163:
Hex says Goddess instead of God. [Yep, started picking up sayings. Funny that THAT is what you guys picked up on!]
Elias notes that Binary has an unrecognized omni-pad. [Ding ding ding, another big clue.]