If you’re like me, you have some dormant WordPress sites that have collected tons of moderated comments. Yes, you could delete these manually, but that can get tedious. At the same time, you may not want to delve into MySQL.
Just tonight, I ran into this issue when I discovered ca. 4k moderated comments on an old site. I quickly locked things down to prevent more from piling up (by setting WordPress to close comments on posts over 14 days old), but I still had to deal with those comments — all of which were spam.
Not wanting to spend much time on it, and not wanting to tinker with MySQL, I poked around for a plugin that would handle the dirty work. Guess what? I found one… Here it is: link.
Simply download, install, and activate the plugin. From there, click the Tools menu, click the Bulk Comment Remove link, and click the button to let the plugin do its thing. That’s it. Problem solved.
While the plugin only guarantees compatibility up to WordPress 3.0.5, I just used it on 3.3.1 without any problems. Good luck!