Empty Comments

I was getting quite a bit of those a while back. Spam Karma ate all of them and the wave passed in 48 hours. Some things to try:

1. Block all referrer spammers with .htaccess:
http://codex.ww.wp.xz.cn/Combating_Comment_Spam/Denying_Access#Editing_.htaccess_To_Deny_Access_Referrer_Spammers

2. Block all connections from pinappleproxy. Add the following line to your .htaccess along with the referrer blocking rules:
SetEnvIfNoCase Via pinappleproxy spammer=yes

3. Give Bad Behavior a shot. After all, why not?
http://www.ioerror.us/software/bad-behavior/