Comment 9 for bug 1668148

Here is the current message:

 Force UEFI installation?

 This machine's firmware has started the installer in UEFI mode but
 it looks like there may be existing operating systems already
 installed using "BIOS compatibility mode". If you
 continue to install Debian in UEFI mode, it might be difficult to
 reboot the machine into any BIOS-mode operating systems later.

 If you wish to install in UEFI mode and don't care about
 keeping the ability to boot one of the existing systems, you have the
 option to force that here. If you wish to keep the option to boot an
 existing operating system, you should choose NOT to force UEFI
 installation here.

And here is what has proposed in the prior upload that was rejected from the queue last cycle:

 Force UEFI installation?

 This machine's firmware has started the installer in UEFI mode but
 it looks like there may be existing operating systems already
 installed using "BIOS compatibility mode". Furthermore, it appears there
 is no EFI System Partition (ESP) on your system. If you continue to install
 Debian in UEFI mode and do not create an ESP, it might be difficult to
 reboot the machine into any operating system later.
 .
 If you decide to force installation in UEFI mode, be sure to create an EFI
 System Partition to make sure your system will be able to boot after install.
 .
 If you wish to keep the option to boot an existing operating system, then
 you should not force installation in UEFI mode.

I understand UEFI fairly well, and both messages are completely unclear to me. What does it mean to "force" UEFI installation on a system that has no ESP? If I am being told to "be sure to create an ESP", is clicking 'ok' going to give me an opportunity to repartition? Or is it going to proceed with an installation without creating an ESP, therefore requiring me to repartition outside of the installer in order to make the system bootable? Or is it going to *automatically* create an ESP for me if I say "yes" to "force", thus making the "be sure to create [...]" message an irrelevant lie? And why are we telling users that they may not be able to boot other OSes in BIOS mode once they create an ESP? If we've detected other OSes, they should be added to our own grub config with os-prober. If we haven't, we shouldn't be printing scary messages about OSes that don't exist.

Someone needs to understand the answers to these questions, and clean up the warning prompt to match.