The system has a feature where if one posts an answer with very short text and an internal link to another post on the site, it will not be posted as an answer, but instead as a comment, telling the user that it's a "trivial answer converted to comment".
However, this feature also works on questions that are locked for comments. It can be used to bypass comment locks to post comments on questions, as one can post an answer that triggers the script and then edit the comment to contain whatever they want it to say. I was able to post this comment using this method:
Note that I took the screenshot after editing the comment; the original content was "this is a test" followed by a link to a random post. Note also the presence of the disabled button to add a comment.
I think this case may have been overlooked since the original lock functionality would block answers to questions, but this specific type of lock no longer does so.
A similar issue was reported for automatic duplicate comments ("Does this answer your question?" comments posted when someone votes or flags to close a question as a duplicate). I think such comments should continue to be posted on comment-locked questions since it's the only public indication that someone's flagged the question as a duplicate, and the user cannot specify custom text for the comment's original revision other than the target, but it should not be possible to edit them after they're automatically posted, since this also bypasses the comment lock.
I'm also unable to delete comments posted as a result of exploiting this issue: when I attempt to do so, I get an error message:
Comments on locked posts are not eligible for voting
Can this hole please be plugged? The trivial answer script should be disabled on comment-locked questions (either such answers should be blocked entirely with an appropriate error message, or posted as actual answers).
