reassign 37254 debian-policy, dpkg severity 37254 normal quit I agree that update-alternatives shouldn't put an alternative into manual mode because a _target_ disappeared unexpectedly. I'll look into this eventually.
But, the problem doesn't happen if you call update-alternatives in the prerm, which is where you should. So it would be good if the policy manual could be changed to this effect. Therefore, I've reassigned this bug to "debian-policy, dpkg". When the policy is changed, please assign it back to dpkg. Thanks, Ian.