I get the sense that it's not a mispelling in the sense that Ariadne doesn't know how kerfuffle is spelled. Maybe I'm reading too much into this, but I also think that the comparison to Ariadne's bunny plushie - i.e. a fluffy thing - is related. Kerfluffle can be read as a portmanteau of kerfuffle and fluffy - a kerfuffle caused by Lee's need for a soft, fluffy thing to protect his ego. Dunno. Deep exegesis that could be entirely off base - maybe it's just a typo.
Kerfluffle is the way I say and spell the word. Wiktionary lists it as a variant:
When you look at the etymology that's clearly a misspelling that has stuck somehow.
Lots of modern English words arose from misspellings (and mishearings) - if one becomes popular, it becomes an English word. That’s how languages evolve, otherwise we’d still be speaking Proto-Indo-European.
Plenty of words are like that. "Apron" was originally "napron" but due to confusion from "a napron" sounding like "an apron" it changed that way.
I personally have always said "kerfluffle", not kerfuffle.
Kerfluffle is a misspelling that has yet to be "standardized", which is why you will only find that misspelling in crowd sourced dictonaries where people have added definitions to justify their misspelling.
I've heard a lot of people pronounce it that way. So much so that I figure it may actually be like 'irregardless' now.
Imagine an ad campaign where disagreements were solved by fluffer nutter sandwiches.