So, my current theory on LE.
The kernelsprites prototyped each other. Caliborn has entered the game, but has not yet been prototyped by the metasprite. At some point, he will go to sleep, and his dreamself will prototype Calliope, say his own name, and then place his dreamself on his in-Derse quest bed and kill his dreamself, ascending to God tier and merging with the metasprite (which may render its prototyping powers nonfunctional, since Jade doesn't seem to have demonstrated many sprite-related powers - she may still have them, but this would at least explain why we haven't seen LE prototype more things, which you would expect the metasprite to continue doing).
Two possible directions from here.
1: Caliborn has been dominant ever since, both as his dreamself and as the waking original body. This is the most parsimonious explanation, probably, and will likely result in Calliope's awakening at Roxy's hands causing a Tavrisprite-esque explosion on a larger scale (utilizing another mechanism we've already seen), since we'll now have Calliope with dreamCaliborn.
2: Calliope was awakened at some point, and their personalities were not all that irreconcilable. This would account for LE's strong associations with the color green (moreso than the red of his cheeks and the color of his blood), his apparently fused typing quirk of perfect grammar in all caps, his proficiency with Calliope's weapon, and any other connections. This would require Caliborn's personality to still be the most prominent, based on LE's actions.
Both of these still leave me wondering about connections between Doc Scratch and Calliope. Last time I mentioned this I also forgot the obvious "They share a body with apparently LE".
I still have no idea about the pool balls.