With the release of WordPress 2.8 development of Yawasp is discontinued!!! For further protection against automated Spambots please checkout the succe
Comment Spam is blocked within the plugin. You don't see it and you don't have to moderate it.
No, the plugin focuses on Spambot-comment-spam only.
Due to the core functionality of Yawasp false-postives are nearly impossible. There might be problems when using Cache-Plugins, but none have ever been reported. If you are uncertain, try puting catched Spambots in moderation queue or mark as Spam (Akismet or similar required).
Check you comments.php. This is very likely because your comments.php has not been setup correctly.
As Yawasp is checking every comment before WordPress handles it, it is possible, that Yawasp catches a Spambot, counts is, but the WordPress comment handling does not accept the comment (e.g. missing Author). As a result, you have catched a spambot, but no comment.