In theory kerning differences would make letter ordering significant, so this becomes a permutation problem not a combination problem, and therefore much harder to brute force.
Is kerning used also across spaces? I.e is the space between two words dependent on which letter the first word ends with, and which letter the second word starts with?
If not, it still seems tractable using dictionary words.
Ok. Makes it much more difficult. Still, assuming grammatically valid sequences of dictionary words, kerning would be known both within and between words. These texts however probably contain lots of abbreviations, footnote symbols, numbers, brackets etc, that make it likely to be a lot harder than just regular prose from dictionary words.
It's been a while since my last discreet math class so take this with a grain of salt, but in a combination you only care about selecting the correct members of a set, so order does not mater. In a permutation problem you care about selecting the correct members as well as their order, so it is a significantly larger solution space which expands factorially.
