The letter ‘K’ as a mark of origin?

[JoJo_Jost]

I understand your question, but that wasn't what I was getting at. And yes, I recognize the 'a' and 'o' in the manuscript as Latin letters, but what we don't know is what the letters stand for. My question was therefore hypothetical, since the spelling in medieval manuscripts might possibly differentiate origins through the function of the 'K' or 'C'.

I think what the previous answers were trying to say, but clearly did not, which is typical for this forum, is the following:
Your question suggests that this should be some kind of substitution cipher. 

Most people here assume that it CANNOT be a substitution cipher. This has to do with statistical analysis, but also with the fact that substitution ciphers are very easy to crack – if normal language were used. For many here, that would be child's play. And since the world's best cryptologists have not managed to crack this code, the prevailing opinion is that it cannot be a substitution cipher. Especially since there are indeed some irregularities in the statistical analyses that clearly contradict this. A substitution cipher would have to be able to explain these, which is difficult.

But I think that the fact that no one has cracked it yet is no proof of anything, and statistics are just statistics. It is common knowledge how easily certain little things can influence statistics. So...