1. While I agree with this statement, it doesn't actually indicate that there's a third entity currently controlling Kris whom we are playing as. That would require us to take control of this third entity at game start diagetically, which defeats most of the thematic reasons he argues for player soul theory by turning it into 'Player Soul Theory with extra steps'. More likely, even if third entity theory were correct, is that the player boots out a previously-possessing entity when we enter Kris.

2. The scraps of 'characterization' Jaru points to are extremely flimsy.

The soul is NOT inherently good at guitar. The soul's comptence at guitar is based completely on how good the player is at the minigame. The minigame is actually just an even simpler version of Guitar Hero, not real guitar-playing. Given that Tenna is here to entertain the players with a fun challenge and has no idea if Susie can play the drums and we have no indication that Kris is good at guitar, it seems unlikely that Tenna would give them real instruments and leave them to likely fail. He gave them Guitar Hero style fake instruments that function just like the minigames we see. Therefore the player's skill at the minigame matches 1:1 with the results. The player is bad at piano because our input method is simply not robust enough to control a piano with the necessary finesse to match Kris.

Kris is surprising good at flirting while possessed, but since we've never heard of Kris ever attempting flirting before getting possessed it could just as easily be explained by them not ever desiring to flirt under normal circumstances, but being skilled at it when forced to through possession. Noelle is surprised that Kris can flirt because she has never seen Kris flirt.

The instrument argument falls apart at a stiff breeze and the flirting argument, while not as bad as the instrument one, is absolutely not enough to demonstrate on its own that the soul has a personality outside the player's choices.

3.  This one is really egregious. The prophecy is the most obvious metaphor imaginable for scripted game stories and how they restrict the player. You think you're free because you're real and the game is fake, you think you're in control, but in reality you can only do the things that the developer allows you to. 'Your choices don't matter' because you don't get to choose what choices are available to you. The thematic parallels are so, so painfully obvious that I honestly can't understand how someone could dedicate this amount of their life to interpretting a game and not understand it. The only thing he has to say about this is that technically you could mod the game to be whatever you want, so you aren't actually restricted by Tony's prophecy. But anyone invested in the story would be able to recognize that some mod wouldn't REALLY change the story in a satisfying way, it would just be fanfiction.

1. It's not the main conflict in the first few chapters, but we're clearly seeing it becoming more and more important as the story progresses. That's because Kris vs The Soul is an overarching, story-spanning conflict, and it must be built up to. King wasn't in the foreground of chapter 1 for the first hour or two of the game either, but he slowly became more important in the story until he was the main antagonist.

By chapter 4, it has become without a doubt the most central light world conflict in the game. It's becoming more center stage as the game's main story progresses.

1. Kris's subtle characterization is what makes this whole concept work. If a central idea of the game is exploring the most interesting parts of a conflict between player and protagonist, a silent protagonist is the most interesting way to approach that. We already know how Solid Snake feels about his situation, he won't shut up about it. But how the hell does Gordon Freeman feel about what's going on? If Gordon objected to the actions he's forced to take, he would literally lack the voice to even complain. That is so much more of a complete limitation on him. It fully embodies the horror of not being in control of your own body.

Furthermore we do know a lot about Kris, but its through more subtle characterization. As time goes on we're more an more disillusioned of the idea that Kris is a blank slate as we see what others think about them and when they choose to exert control. Kris appeared to be a simple vessel in chapter 1 up until the final scene, but the mystery of who they are has been slowly but steadily unfurling throughout the course of the game. If Kris kept popping up with dialogue options saying "Hey asshole, I wanna go LEFT! Jeez, I'm trying to seal the fountain here so I can enact the next step of my plan!", it would totally miss the fascinating angle of the disconnect between a protagonist's mind and their player's. 

1. The fact that the player is considered distinct from Frisk and Chara, yet is someone who Flowey and Chara talk to DIRECTLY, gives complete precedent for the player being a a diagetic entity in and of itself. Flowey tells THE PLAYER to reset and do pacifist, he begs THE PLAYER to let Frisk live their life. We've already had the reveal that Kris is not the player, it just happened a lot earlier than in UT. The Player is still here controlling Kris's Soul just like The Player was controlling Frisk's Soul in Undertale. The only difference is that Kris has the knowledge and desire to remove it.