[Caerus]

I'm not sure which part you're asking about. I'm assuming it's that "correcthorsebatterystaple" is only lower case.

I was mainly commenting on the format suggested by the comic - 4 all-lower case words. You could throw in capitilzation, but most people are going to follow some pattern such as capitilizing all the words or the first and last, etc. These schemes only add a couple extra bits. Fully random capitilization would greatly increase the strength but make it nearly impossible to remember.

There are a lot of assumptions in these calculations, chief among them already knowing the format of the password. It's somewhat reasonable to ignore though, because not knowing the format of the password is going to add extra complexity more or less evenly across all formats.