One of Karkat's parental figures is a believer in Men Don't Cry
In an ask post, Karkat mentions that when he expressed emotions honestly, they were used against him in some unspecified way, which seems, from the phrasing, to relate to personal identity. Karkat is a trans guy. Maybe he was told something like "if you're not a girl, stop acting like one" every time he became visibly upset in a non-ragey way? The relatively unsympathetic portrayal of Vriska's issues is actually some deliberate secret meta trolling scheme.
This is Vriska, remember. Base Breaking Characterdom may well be endemic to her nature, even across species and universes. Aradia is dead.
Sollux still hasn't gotten over her dying, and is in pretty heavy denial—hence him talking about her in the present tense—but she's still dead, which is why no one at St. Lobaf's has ever actually met her.
Like in canon, Bro will actually be Dave's biological father
And this will come out when someone does a court ordered DNA test, possibly without either knowing. Might be the final nail in the coffin as far as Bro's guardianship of Dave goes if it turns out it was something like a Family Relationship Switcheroo and they lied about it and fabricated documents. Calliope's burns were caused by a Brainbent version of Caliborn
It would only make sense, what with Caliborn being the abusive Big Brother Bully he is in canon. Equius's family are Parsis.
He has dark hair, Zahhak is a Persian word, and a lot of Parsis are businesspeople, like Equius's dad. Calliope's fear of the Felt/Leprechauns is Caliborn's fault
Okay, I theorize that basically everything bad in BB!Calliope's life is Caliborn's fault, but for this example specifically; he convinced her that there were a bunch of scary, evil monsters who are following her around and watching her, all just to scare her and mess with her mind. Davekat will be canon in this AU, similar to how it's (kind of) canon in Homestuck
Dave and Karkat are roommates and pretty darn close. It also certainly doesn't hurt that Dave's a-okay with Karkat being trans. Caliborn will finally appear in the blog and then...
...he'll get into an argument with Gamzee culminating in Gamzee punching him in the freaking face for bullying Calliope like he did. Bonus points if it comes after Caliborn reveals that he's the reason Calliope is burned.