Cloaca
I suggest adding in a system where that even if a player is not in your friends list, that you can still block them, so that they cannot PM you anymore. It doesn't really make sense to me that you have to have them as a friend to block their incoming messages. Perhaps adding in a /block [insert player name here] function into the chatbox? Just to get rid of the fact that you have to disable PMs entirely to avoid getting messaged by people possibly annoying and/or harassing you.