Bored on the Internet as I tend to be, I have developed an idea I call, unsurprisingly, "The Parson Threshold." It refers to the moment when a character in a fictional work has a moment of sudden realization that frees him from a self-imposed mental block, when a person first starts to realize that other solutions besides the obvious one are present. (Parson crossed this threshold before the comic started, lateral thinker that he is. Of course, nobody's perfect...)
Jack crossed the Threshold here,
for the first time on-panel at least. It happens in Panels 10-11 (and presumably off-panel in 12, depending on how that chronology works). Jack applies what he's learned from Parson to find an utterly unconventional yet utterly simple solution to their current predicament. Since this paradigmatic progression is sort of the whole plot of Erfworld, Jack's pretty much the only one who's broken out of his box. (Not that he had much of a box to begin with.) Tramennis is clever enough to learn and adapt in this fashion, should he encounter Parson at a time when they are not trying to murder each other, but that's gonna take some doing. Assuming Tramennis even lives through this battle, which I do hope he does.
Another example from another popular fantasy webcomic that everyone here has almost certainly heard of: Order of the Stick. Vaarsuvius has hir* epiphany here
right in Panel 8. V has completed that manner of frustrated rant many times throughout hir career, so to see hir suddenly catch on is quite gratifying. Between V's Awesomeness By Analysis
to deduce the nature of the gap in hir rival's defenses to hir finally using hir awesome capacity for monologuing offensively
rather than just incidentally, V has taken another step closer to approaching the buzzing, humming, unconstrained cognition that powers the good Lord Hamster.
* When is the English language going to freaking decide on a standardized polite gender-neutral (or gender-ambiguous) third-person pronoun? "It" can't really refer to people and "his/her" just wearies me.