Greg had the same idea and abstracted the main messages of the thread onto his website and has added some further speculation on Kaighin origins.
I am still searching for a definitive cause of the C,K, Q name standardisation - I can not believe it was down to coincidental fashion or dialect change in naming or recording - there would have been more Mac**** names surviving if this had been the case - the almost universal transformation of the Mac prefix over a relatively short period to create the distinctive Manx surnames that we all know and love suggests an active ingredient, possibly of a legal nature (as in Ireland) to force greater English influence in the Island and reduce the Irish/Scottish culture (in the context of Lancastrian rule of the Island, continuing strife in Ireland between English and Irish and the Manx/Scottish reciprocal 'raids' at the time).
I am still hoping to find, or learn of, a prompt/cause - but considering those days of 'breast-law', minimal literacy and the subsequent survival of few of the records that were created etc, I am not too optimistic!