Then, importantly, it collapses itself back down to a 1-dimensional copy of its starting representation, but translated.

Specifically, after 133_076_755_768 steps, the 1-dimensional pattern reoccurs translated by two pixels. On skimming the thread I haven't determined if that shift is parallel or perpendicular to the line.

I think it has to be parallel by symmetry.

Can it leave other bits behind after it moves?

By definition of a pure spaceship / glider, no it can't. If it emits persistent "exhaust" that's a "smoking ship"[0].

[0] https://conwaylife.com/wiki/Types_of_spaceships#Smoking_ship

IIUC, "smoke" is ephemeral by definition. A spaceship/glider that leaves persistent "debris" in its wake is called a "puffer":

https://conwaylife.com/wiki/puffer

Smoke refers to fairly long lived debris that eventually dies out, the term for one that leaves permanent debris is a puffer.

No, if it does it's called a puffer.