Okay, this is just absurd now. I did the diff and other than the presence of hijack.c.orig in one of the trees and not the other, there were no other differences.

To prove I'm not insane, I built kernels out of both trees. The one built from the v300+42 patches tree gives me notify output, the one built from the v342+2patches tree doesn't give me notify output. In both cases, all I did after running the patches was copy arch/arm/defconfig to .config, make config, and make zImage.

The mystery then becomes how two identical source trees (or at least identical according to "diff -u --recursive --new-file --exclude=zImage --exclude=config.ini --exclude=.* --exclude=*.patch --exclude=buildit --exclude=defconfig --exclude=hijack.c.orig v300 v342") can yield two different kernels. I'm calling Unsolved Mysteries on that one.