bug#52539: Fwd: Comments in /etc/passwd don't get updated

[Jacob First <jacob.first@member.fsf.org>]

In my Guix system's /etc/passwd file, my user named "abc" has a
comment attached to it. The relevant line is:

    abc:x:1000:998:Old
Comment:/home/jkf:/gnu/store/71yp1p06jy2j96bfdz43f4p6ncdym5a1-zsh-5.8/bin/zsh

Today the users section of my current config.scm looks like this:

    (users (cons* (user-account
                    (name "abc")
                    (group "users")
                    (comment "New Comment")
                    (supplementary-groups '("wheel"
                                            "netdev"
                                            "audio"
                                            "video"
                                            "disk"
                                            "cdrom"
                                            "docker"
                                            "libvirt"
                                            "kvm"))
                    (shell #~(string-append #$zsh "/bin/zsh")))
                   %base-user-accounts))

After I apply this configuration with `guix system reconfigure', I
expect /etc/passwd to have been updated with "New Comment" in place of
"Old Comment". However, "Old Comment" remains.

Similarly, if I omit the `comment' field entirely, I expect my user
comment to be removed from /etc/passwd, since the default value of the
`comment' field is documented to be an empty string (manual 10.6).
Again, the old comment remains.

I am reporting this on a recent Guix version cev9c6c5, but have
noticed this issue for a year at least.