What are WordPress trash comments and how to clean them?

A trash comment is a comment that you have deleted from your WordPress site and have been moved to the trash. A trash comment is not visible in your site and should be deleted forever.
You can either use our plugin Advanced Database Cleaner to clean-up these trash comments or execute the following SQL code (which is used by the plugin) directly via your phpMyAdmin:

DELETE FROM comments WHERE comment_approved = 'trash'