Tired of spam.
Even though WP blacklist worked fine, I still got a lot of comments/spam in the “awaiting moderation” menu, and had to check all of them to avoid errors in the filtering.
Now I installed Trencaspam, a hack that inserts an image with a code you have to type when submiting a comment.
Now that I changed my hosting provider it all works fine (with the previous one I did not had the last PHP version and could not create dynamically the images). Hope it works also for spammers.