user/group removed by upgrade

When upgrading Kubuntu 9.10 to 10.04, the subversion group/user with which an svn server was running was removed. Looking at the logs showed that an update-passwd process did this as part of the upgrade. Silently deleting users/groups from a system is something I'd put on the 'don't do' list of upgrades. Specifically, the Ubuntu subversion server howto guide includes the creation of this user/group - if this is flawed in some way, it would be a good idea to update the guide.

Expected behavior: if there is indeed a compelling reason to remove users or groups from a system, the upgrade process should present those reasons, followed by a prompt asking the user to confirm the action or skip it.