Thanks for reporting this issue and for providing steps to reproduce. I tried to reproduce it on Ubuntu 22.04 (jammy) and added a "#--ariel--#" comment line to my sudoers file. sudo correctly ignore it. So I mark this bug as fixed.
** Changed in: sudo (Ubuntu) Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to sudo in Ubuntu. https://bugs.launchpad.net/bugs/501204 Title: sudo syntax error in /etc/sudoers due to #-- comment Status in sudo package in Ubuntu: Fix Released Bug description: Binary package hint: sudo I put a few comments in /etc/sudoers where the '#' comment char is succeeded with -- as in: #--ariel--# result: sudo won't work anymore. $ sudo echo OK >>> /etc/sudoers: syntax error near line 9 <<< >>> /etc/sudoers: syntax error near line 27 <<< sudo: parse error in /etc/sudoers near line 9 sudo: no valid sudoers sources found, quitting putting a space between the '#' and '--' solves the problem. Comments should start with '#' only. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/sudo/+bug/501204/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp