Comment 10 for bug 1893906

To help this case going forward I ensured there is an easy repro for anyone to try.
The following works well on a clean Ubuntu (and most likely any) install.

$ sudo apt install smbclient samba
$ mkdir /tmp/testshare
$ sudo chmod 0777 /tmp/testshare/
$ cat << EOF | sudo tee -a /etc/samba/smb.conf
[testshare]
   comment = Test bug 1893906
   path = /tmp/testshare
   browseable = yes
   read only = no
   create mask = 0700
   directory mask = 0700
   valid users = ubuntu
   guest ok = yes
include = /etc/samba/test1.conf
include = /etc/samba/test2.conf
include = /etc/samba/test3.conf
include = /etc/samba/gtest1.conf
include = /etc/samba/gtest2.conf
include = /etc/samba/gtest3.conf
EOF
$ cat << EOF | sudo tee -a /etc/samba/test1.conf
   comment = Test bug 1893906 - 1
include = /etc/samba/test1b.conf
EOF
$ cat << EOF | sudo tee -a /etc/samba/test1b.conf
   comment = Test bug 1893906 - 1b
EOF
$ cat << EOF | sudo tee -a /etc/samba/test2.conf
   comment = Test bug 1893906 - 2
EOF
$ cat << EOF | sudo tee -a /etc/samba/test3.conf
   comment = Test bug 1893906 - 3
EOF

The overall structure we now created is like:
smb.conf
 \- test1.conf
    \- test1b.conf
 \- test2.conf
 \- test3.conf

$ sudo systemctl restart smbd
$ smbclient -L 127.0.0.1 -U ubuntu%ubuntu | grep testshare
 testshare Disk Test bug 1893906 - 3

We see (and can experiment with) the comment that is just nicely set in each case.