I've mostly been thinking about UU's identity. Apparently it's a female according to the wiki. I'm not convinced, seeing as how the literal meaning of "Uranian" means a man who behaves like a woman. I'm going to call it a "he" from now on for simple convenience.
I'm sure it isn't a new troll. Why? Recall Scratch saying that there were 24 troll heroes total, no more no less. Which means UU is one of the ancestors or maybe one of the other trolls (possible because UU knows a lot about future events, so much that a few Prospit clouds won't do). It's true that anything Scratch said can't be trusted at this point, but he still doesn't outright lie.
It's confirmed UU is one of the players, as he said he's about to play SBURB/SGRUB (or was, you know, time shenanigans). Unless he's lying, but I don't see why. He's also been awake on troll Prospit for most of his life.
There's also only 2 kid sessions and 2 troll sessions, meaning this post-scratch alternate universe is the ancestors' session.
My conclUsion? UU is the Sufferer. There's many things pointing towards it: his ancestor name is the Signless, as Ophiuchus doesn't appear to exist in the "violent" troll universe. He bears no sign. And this: "All of the troll's trollian handles are made of letters that represent chemicals in DNA (T, C, A, G). U is a letter used to represent chemicals in RNA, a DNA variant." pointing to the Sufferer's mutant blood. UU also uses gray text, and speaks in a somewhat similar style as Karkat except of course being nice and supportive, a Sufferer trait; he's troll Jesus.
So yeah. Those are my thoUghts :U
(sorry for the long post)