List of proverbs and sayings in the Edge Chronicles collected so far by DeadlyDirtBlock, The Strange Traveler and Gloamglozer:

Proverb Equivalent Person Appearance
"bag of leechfleas" bag of fleas Stormchaser
"May earth and sky be with you!"
"If those ... aren't ..., then I'm a jack-stacking leafhopper" Tweezel The Lost Barkscrolls
"Only the sky knows" Common saying among sky-scholars
"Thank Sky for that" Quint The Curse of the Gloamglozer
"was mown down like glade-wheat before a scythe" narration Clash of the Sky Galleons
"Barkworm" derogatory manner for someone inconsequential/powerless
"Hold your prowlgrins" Ferule Gleet
"The hotter the fire, the lighter the dough" Welma Thornwood The Curse of the Gloamglozer
"What you feel is what you feel" Welma Thornwood The Curse of the Gloamglozer
"Goblin stolen your tongue?" "cat got your tongue?"Used when someone isn't saying anything when you've asked them a question. The Last of the Sky Pirates
"skycur" used to describe sky pirates
"Plain as a soot-frog in a snow-pond" Used to describe something obvious Old Torp
"... like a woodcat on a weezit" It's used to describe when someone quickly jumps at an opportunity. Bungus Septrill The Curse of the Gloamglozer
"A couple of raindrops short of a shower." Used to call someone stupid Raintasters and Cloudwatchers
"In death there is life." Tweezel
"May the spirit of the great curling-horn watch over you" Chert to Cade before the Battle of the Farrow Ridges Doombringer
"Sky-touched" someone who is crazy. Used to describe an academic telling conspiracy theories about rats being cooked in the refectory of Sanctaphrax. The Curse of the Gloamglozer
"Sky-fortune has shown down upon you" someone was blessed by fate Wind Jackal to Linius Pallitax The Curse of the Gloamglozer
"Better answer with silence than with indignation" Saying Quint acts upon The Curse of the Gloamglozer
"Crazier than a square circle" very crazy a mobgnome about that academic with the piebald rat conspiracy theory The Curse of the Gloamglozer
"Quicker than the Chorus of the Dead at a funeral" very quickly Professor of Light, how quickly the academics will turn on Hax if the Great Storm doesn't come The Winter Knights
"A tilder doesn't change its stripes." "a leopard doesn't change its spots", used to describe Heft, means that a person can't change their personality no matter how hard they try Maris The Winter Knights

Maybe this can be made into a real article in the form of an alphabetical list that states the proverb, the English equivalent, who said it, when, in which book, and then links to all the animals that were used for comparison/metaphorical reasons.