I'll admit it, I've been stalking Jess' profile. But I found they've been talking to others as well, not just us. 

I have a few links to different chapters in different theory books. 

First off--  

https://www.wattpad.com/414142550-just-a-place-where-i-post-randomness-theory-for

So what Jess (the author this time) is saying is that she knows of his presence, and allows him to talk to us. She doesn't care that we know of  him, she cares that we know who he is.
    (Also this is a pretty good theory about why Felix was crying.)

Secondly-- 

https://www.wattpad.com/415392915-theories-on-useless-ugly-sob

I got some screenshots of this.

"Scream and Go"

"Surrounding" 

(He got irritated and left sooner or later, and I don't think he'll be going back there, meaning we can't get anything else from that)

And Lastly-- 

https://www.wattpad.com/415089657-theories-on-useless-revise-it-all-together

"What we have"

[This is a list of what we've basically gathered so far.]

"What we've collected until now.
-Billy has multiple powers
-there are two people infiltrating jess
-Billy has some sort of grudge
-Aaron is M.I.A
-Nate is also M.I.A
-Nate appeared, messing everything
-Aaron too appeared, then disappeared.
-Felix was given responsibility of someone
-that someone and by whom is unknown.
-possibilities of MAD/VIRUS Cry
-Cry knows way too much
-Video game dude+

Aaron
He went missing in action then was never to be seen. He was previously Mark's mentor and had ice-manipulation powers

Nate
He also went missing in action and his power is gravity manipulation. His position is apparently minion. Has some connections with Mat

Billy
Is biased over Jack and claims to be his all time fan. Doesn't like Mark as much. Literally sensed 'zalgo' and punched him in the face like a bo-- Okay I'll stop. Has multiple powers for reasons unknown. Has a literal grudge and literally tried to kill Mark when he confessed to Jackaboy. Well, not really confessed bu-- and last but not least, SCREW YOU BILLY

Felix
He was given the responsibility to look after someone and had claimed to apparently be not appropriate enough and legit cried all day in the music room. Whoever that is or whoever gave the responsibility, we do not know. It is assumed that he is younger (by me) so the only options are Robert and Billy 

Cry
This guy has eavesdropped on many things more than we would like to know as he says in literally every chapter. So it's obvious he knows a lot. Seeing that Cry is comfortable with his face open to Felix, (eyoo shipple) assumptions are made. The let's play a game thing had Ceaser's Cypher on ROT 19 and it said out Cry's very description irl.
Keep in mind that it's 'the last line' where else have we seen this? that's right, "all you have to do is look at the last lines"
Well, we did, it seemed to be describing someone but idk..

Virus/Mad Cry
Cry's alter ego in his videos that laugh like really freakily and that also crashes games due to an unknown virus aka virus Cry. We don't really know much about him but assume that it is most likely virus Cry who got into Jess' account and blurted all of that out. They say that they're only trying to help or whatever but that is quite a mystery.

Simple job
This guy points out that he likes Jack's and Mark's scream for some reason. (Freak) and also is interested in Billy because apparently he can 'sENSE' him.
And 'sEE' him.
Who the frick goes invisible?
That's right.

YOU KNOW THE FLIPPING ANSWER!!

Delsin
The video game dude who was in the incident where the child was trapped but oh, key word, he didn't harm the child one bit! Neither did he harm Jack. Who did he harm though? Troye and Mark!
Why not Jack though?
What's Jack's power though?

WHAT YOU PLANNING, ERR, ERM.. REALLY FREAKY FONT DUDE."

Word for word.