itch.io

Individually, the facts point to TJ being the one who wrote the letters, but taken together they begin to clash with each other. When TJ attacked Carl, it ruled out the possibility that TJ was aware that he was the one who wrote the letters (since he wouldn't have directed his anger specifically at Carl in that case because he would have known the letter was fake). 

However, this then throws the other parts of the theory into question. If TJ did wrote it all unconsciously then he would have had to write the letters in Sydney's style, made the letters look old, go around town to place the letters, all the while unconscious. It was also strongly hinted that the letter in the school building was unnatural, and that it would have been looted years ago if it was really that old (which puts doubt onto the theory that TJ made the letter before the trip). 

Then there's the matter of the clues themselves. The clues are passively hostile towards Chase, suggesting active dislike or hate towards Chase (which only really Sydney and perhaps Flynn feels that way, more on that later). Given what we know, I find it hard to believe that TJ would come to hate Chase subconsciously. TJ has always hated Sydney so there would be almost no reason to hate Chase after Chase saved him from drowning. And if it was subconscious, we would have seen some hint of the hate bubbling up into his consciousness every now and again. TJ may have held the pain and guilt, but hate just doesn't make sense for him.

"if anything the entity controlling Chase was pushing him towards concealing the truth not revealing it"

Did it though? We don't know for sure if TJ would have told Flynn the truth, all we have to go on is the entity's words (and it lied about Flynn knowing Chase's secret, and also about breaking the cycle by killing Flynn). And the reason it helped Chase was probably because it didn't care about revealing the truth, but in getting hysteria events to happen. Taking the other routes into account, TJ's route is very unique because of 2 things: 1) it's the only route in which the hysteria didn't happen in 2015, and 2) it's the only route in which the entity speaks directly to Chase. 

With the hysteria, I think it's because this is the only route in which the group is completely destroyed, splintered apart. So if the truth were to be revealed, it may not have been enough to cause the required emotional reaction for the hysteria that the entity wanted - so the entity decided to cut its losses and prepare for the next hysteria (by creating a new secret for Chase to hide). Evidence for this can be found with Flynn. As he was dragged under water he realized the truth, yet the hysteria didn't happen because his emotions alone wasn't enough (based on information from Murdoch's route in TSR, the entity feeds on emotions).

As for the other unique thing with the route, the entity during its talk with Chase admits that the town is almost saved, that it may actually survive. Or in other words, its plan was almost foiled. From that information, it is my current theory that it was the socket monster who wrote the letters. 

Remember how the clues contained a dislike for Chase that only Sydney had? What if it was actually Sydney who wrote them as the socket monster. From Flynn's route we know that the socket monster is an amalgamation of multiple people/entities. And just before Flynn was absorbed himself he got to meet Sydney, suggesting that like Flynn, Sydney was absorbed into the monster. And we know from Jenna that the monster has always been there for her and protected her, which would give it a motive to foil the other entity's plans. Looking at the result of the letters, the letter was at least successful in getting Jenna checked out of Echo early and out of harm's way.

And if it was the socket monster, a couple of other random details just falls perfectly into place. Being a supernatural entity, the monster could have easily forged the letters on the spot and made them look old and placed them anywhere anytime. Being another entity like the one that spoke to Chase would have also given it the power to oppose another powerful and manipulative entity.

That said, the theory does have a couple of small holes that I've yet to work out. The biggest one would be how close the letters drove the town to hysteria. If the socket monster's aim was to protect Jenna and perhaps stop the hysteria from happening, it came very close to triggering the hysteria through the final letter. If Chase hadn't swapped out the final letter, there was a real chance that the reveal would have caused a hysteria similar to the one in Flynn's route. So does that mean the monster knew that Chase would swap the letter? Or did it manipulate Chase into swapping the letter? The other issue is that if Sydney is conscious as the monster, why does it protect Jenna? Why not someone else like Flynn?

Of course, my theories regarding the entities are far from conclusive. We'll likely have to wait for Arches to get some concrete information on them :/.