Suzanne Kemmer sent along this example from a web forum:
I read on the internet that this means he mightened get along with another rabbit. [emphasis added]
I don't think that I've seen this before.
But it's out there:
I hadn't considered the fact that my Junior mightened fit into a Les Paul Standard case.
Do you hold back on giving your opinion because you know someone else mightened like it?
Oh, and something people mightened have noticed, Arctic Monkeys beat every Beatles album, ever, EVER.
Ive deleted heaps of stuff of my computer cause i thought there mightened be enough space, but it still wont work.
this mightened make a whole lotta sense but if your bi and want to score guys whats wrong with gay guys?
The horse owner mightened mind you not having a stable but I would think you should try to have one of some description.
Its happened to me twice, it mightened be a case of Dragonless Dragonstorm but I'm pretty sure it is.
I mean, after all, he mightened have known what constitutes pure happiness and hence wasn't afraid of having sex with Buffy later and got a rather big surprise?
Does the re-analysis make any sense? Well, might is technically the preterite form of may, mostly used in these cases for "modal remoteness". So re-analyzing "mightn't" as might+en+ed gives it a slightly more regular-seeming preterite form (with the irregular form in there too, just in case, like the kid who holded the baby rabbits). And perhaps 'en' is seen as a funny way of spelling the 'n' of a contracted negation.
So I guess, in retrospect, it's not totally unexpected. But if you'd asked me, I wouldened have predicted it.