I'm pretty sure I saw this option when I was messing around on settings once, but if this option doesn't actually exist, feel free to lock this thread.
Anyway, I'm assuming that they are no longer able to send you messages (VM or PM), but does it also go a step farther to hide their posts on threads? I know that gameFAQS has a block option that does that.
Basically, I'm just wondering about the extent to which a user is blocked.
The option does exist, if you go on a user's profile, on the left there is written" add to block list" or something like that. All it does is that the person you'll block won't be able to add you as friend, they can't see your visitor's message, they can't PM you and as for you, you won't see the person you blocked's messages. (In a thread)
That's all I remember about it