Looking for Group has Tim, a none-too-bright troll who at one point uses "DIS MY INSIDE VOICE" as a warcry. That may have also been his internal monologue.
Philia, Phobia's sparring partner from her Amazon days, in GastroPhobia.
Philia:AND ANOTHER THING, WHAT'S THE DEAL WITH PHILOSOPHERS? Klepto:(whispering) Was she, uh, always this... loud? Phobia:(whispering) Yeah, I must've had a much higher tolerance for whining as a teenager.
Karkat isn't the only troll who incorporates at least some all caps text in his chats and speech, but he's the one who best plays this trope straight.
Equius is assumed to often fall within this trope, even though he uses all caps sparingly.
If Homestuck partially defines this trope as a character who types or speaks in some variant of all caps, then Tavros and Terezi subvert it. Ax-Crazy Gamzee falls within this trope half the time. The WV, the AR, and other Exiles speak like this in the kids' and trolls' heads at times.
Stand Still, Stay Silent: Sigrun does have a few settings on her volume dial, she just forgets which settings are appropriate for indoor use when she gets excited. She even manages to out-shout a hall full of feasting Norwegian berserkers, and gets shushed down by her mom.Case in point.
In Champions Of Faraus,the God Parthelax always talks like this.Combined with the lack of a greeting in the second story arc, he (unintentionally) scares Flamel when he jumps into a conversation about traveling on a mountain road.
Parthelax: HARPYS THERE HAVE ATTACKED TRAVELERS LATELY.
Flamel:(while looking shocked and shaking)Who-who's that?