Isn't some of Japanese writing vertical? Might help me learn.

Imagine trying to read that

Kernel code is very often a series of short words, and very often formatted to take a lot of vertical space (i.e lines of code). It can be hard to read, especially when it's a short code that corresponds to a longer function or location; but with practice we can cope.

tho

See? You're expecting people to do it already. And kernel code conforms to the grammar a lot more than American 'english.