Bug#602788: live-boot-initramfs-tools: live-getty and serial console is not working as expected
This is affecting me too. FYI, you can test serial support for a live image with something like:
$ qemu -hda binary.img -serial stdio
Serial console then appears on the command line.
I've poked around to try to fix it (or work around it), but haven't really gotten anywhere. Any tips on where to start?