There are two issues:
- Debian policy dictates how home directories are managed and properly packaged .deb should not modify anything in users home directories.
9.2.3. Non-existent home directories The canonical non-existent home directory is /nonexistent. Users who should not have a home directory
should have their home directory set to this value.
The Debian autobuilders set HOME to /nonexistent so that packages
which try to write to a home directory will fail to build.
10.7.5. User configuration files (“dotfiles”) The files in /etc/skel will automatically be copied into new user accounts by adduser. No
other program should reference the files in /etc/skel.
Therefore, if a program needs a dotfile to exist in advance in $HOME
to work sensibly, that dotfile should be installed in /etc/skel and
treated as a configuration file.
However, programs that require dotfiles in order to operate sensibly
are a bad thing, unless they do create the dotfiles themselves
Furthermore, programs should be configured by the Debian default
installation to behave as closely to the upstream default behavior as
Therefore, if a program in a Debian package needs to be configured in
some way in order to operate sensibly, that should be done using a
site-wide configuration file placed in /etc. Only if the program
doesn’t support a site-wide default configuration and the package
maintainer doesn’t have time to add it may a default per-user file be
placed in /etc/skel.
/etc/skel should be as empty as we can make it. This is particularly
true because there is no easy (or necessarily desirable) mechanism for
ensuring that the appropriate dotfiles are copied into the accounts of
existing users when a package is installed.
See : https://www.debian.org/doc/debian-policy/ for details
- Installing .deb requires root authorization and packages can run pre and post install scripts that modify files in home directories in violation of debian policy or people who package .deb may choose to ignore debian policy.
So it is possible for .deb to violate debian policy and alter files in user home directories.
This is one of many considerations or reasons you should be very careful when installing .deb from outside the Ubuntu repositories.