ON BOARD WITH THIS. I've written about transfeminine symbolism elsewhere so I wanna focus on a potential piece of transmasculine symbolism I picked up on. TL;DR It's boobs (and their negation). In much the same way that transfemininity can be implied through veiled allusions to dicks (eg Vriska's eye-patch being borrowed from the pirate One-Eyed Willie) or castration, I think transmasculinity can be implied through veiled allusions to breasts or mastectomy. My thought process, by character:

MALLEK. Remember Mallek? Handsome cerulean hacker from Friendsim. Everybody lost their minds when he took his shirt off at the end of the good route because 1. handsome and 2. he had nipple piercings, reigniting unresolved debates about why the fuck trolls even have breasts. The speculative weight of this reveal was quietly seeded earlier in the story when we saw a box of cereal in Mallek's apartment ("Fury Pops", a play on Corn Pops), invoking the question of milk. Made me wonder if the name Mallek was itself a play on milk (also ofc Rami Malek, who then played a hacker on Mr. Robot) ... and made me wonder about his horn piercings. The horse dicks on Horuss and Zebruh ensured that many people read the vague erogenous-zone coding of troll horns as phallic, but Mallek suggests they might be papillary.

EQUIUS. Again, the art on his wall of people being crushed by giant horse penises might lead you to think that the udder on his mustachioed centaur is cock-coded, but if you ignore the pornography and the disjoint between Aurthor's horse/human parts, we're being pretty straightforwardly presented with a milk-producing man. That which dangles below, the "centaur's testicles", are breasts. And if we accept Mallek's suggestion that horns can be papillary, Equius's broken horn fits his archery theme: the Amazons (mythic tribe of all female warriors) in some tellings cut off one breast as a means of improving their archery.

CRONUS. Both of the Amporas have a seahorse lusus and with him the suggestion of male pregnancy; Cronus redoubles this with a name that invokes a god who, in another sense, likewise had babies in his belly; and Cronus being humankin, outright describing his dysmorphia in terms of being born in the wrong body, also gestures at a desire to cut off his horns, which per the above would generate the "dual scars" of a mastectomy.

KARKAT. There is so much I could say about Karkat but lemme start with a manifestation reading of TROLL THIS WORTHLESS HUMAN. To rip some words off my blog, I’m inclined to view Karkat as like, the vengeful ghost of Nanna, in this instance? His anger towards John started with his killing of Nanna during the preceding flash, he ends with “FUCK YOU AND THE JOKE BOOK YOU RODE IN ON” (which killed Nanna), and there are odd parallels posed between Karkat’s “hate” and like, breast milk. “IT IS A HATE THAT TO FATHOM MUST BE PUT INTO SONG. // SHRIEKED BY THE TEN THOUSAND ROWDY SHOUT SPHINCTERS PEPPERING THE GRUESOME UNDERBELLY OF THE MOST TRUCULENT GOD THE FURTHEST RING CAN MUSTER,” Karkat says. “Sphincters peppering the underbelly” is a grotesque picture of an udder, with hate squirting from the teat. Hussie actually painted Horrorterrors as mothers in a news post that same year, describing a squid-orphan who will “never know the taste of its dead mother’s heinous teatbrine” – Karkat echoes this angle, it seems to me. So when Karkat poses his “pure and hot” hatred as a holy gift to John I’m sort of imagining Karkat aggressively trying to put his tit in John’s mouth.

The milk angle explains the phrase “WHY WOULD I GIVE A PUNGENT WHIPPING LUMPSQUIRT WHAT YOUR NAME IS.” – Karkat is conjuring a teat (lump) whose milk (squirt) has soured (pungent) into (whipping) cream. That this replaced the standard phrasing “give a shit” I think recolors Karkat’s next major gross-out, “YOU ARE SUCH AN IGNORAMUS I COULD SHIT MILES OF RAGE SNAKE TO CHOKE YOU TO DEATH.” It sounds kind of like aggressive mothering again, like Karkat is threatening to silence Egbert’s cheeky throat with white hot “hate” straight from the blubbery faucet. Pacify that boy! Pap pap papillary.

ANYWAYS this all obviously isn't exhaustive (eg there are other viable body readings of "dualscar") but it's an angle I'm pursuing at the moment. Very interested in the Isabella Roselini vid, I will check that out