Hello, I like the comic so far, seems like an interesting idea! I have a couple of questions though
What caused Dream's transformation? Was it his sudden moment of growing up/coming of age or is it like a main character/determination moment?
Also, this one may be a bit stupid, but why exactly is Ink mad? I mean, is he upset that Glitter!Dream is similar to something specific (like Superman, or One Punch Man, or whatever), or is it just Dream's inspiration by random fanworks? I dunno, it just seems like some sort of reference to me
Glitter himself is symbolic of both Dream's determination and growth from his prior circumstances as mentioned in part 6. He wishes to move forward in a constructive, driven manner even if it gets hard. His distress from earlier in the chapter doesn't take away from the fact he's willing to confront Nightmare for the sake of the people around him and the emotional balance.
As for the transformation's cause, think of it like a hypergolic fire. They are where two flammable sources can ignite without the need for an external ignition source or oxygen. Dream has a set amount of this from the emotions he gathers passively and the golden apple within him. The latter is why positivity can exist to begin with and granted Dream additional powers he uses to protect it.
One of these he learned over time is that he stores additional positive emotions through his empathy powers. He was able to shape the additional positivity into the arrows he fires by more actively gathering them from his surroundings. Instead of directing his inner hypergolics to light the positivity and shooting the resulting flame at a foe, Dream is absorbing a lot more over a farther range and burning it within himself. It takes a lot of fuel to have the inferno he wants, hence why it took much of part 8 to reveal. Glitter is the end result of this, and it will still take continual fuel to sustain. Eventually, Dream won't have enough positivity in the immediate area to sustain it, and it could be snuffed if his access from adjacent timelines and worlds is cut short.
Regarding Ink's saltiness, he finds the name uninspired and not a good fit for the form. Additional salt is from the fact he couldn't sense it coming due to it being outside of Dream's original creation. Dream defaulting to his fanfics in the heat of the moment and pushing it off in his priorities certainly doesn't help, understandable as it may be. It wasn't any particular reference from what I can recall aside from fandom satire. Either way, Ink will be stewing about this for a while.