This happened to me because I did not grant the site’s MySQL user DROP/TRUNCATE permission for security reasons. I saw this in the server’s PHP error log:
[25-Sep-2014 10:55:37] WARNING: [pool www] child 21991 said into stderr: "NOTICE: PHP message: WordPress database error DROP command denied to user 'username'@'localhost' for table 'wp_wfHoover' for query truncate table wp_wfHoover made by wp_new_comment, wp_allow_comment, apply_filters('pre_comment_approved'), call_user_func_array, wordfence::preCommentApprovedFilter, wfScanEngine->isBadComment, wordfenceURLHoover->cleanup, wfDB->truncate, wfDB->queryWrite"
So the TRUNCATE
command was never actually successful. Is this error caught by Wordfence and displayed in the UI, or is it silently ignored? I don’t really want to grant the TRUNCATE permission to a database user used by a web site.