i think he didnt upload the right second one,he did the same screenshot twice, i think what he is saying is so people cant say something to you then block you, or unblock you, message you, then block again, facebook has limits so if you unblock someone you need to wait a certain amount of time before you can block them again, and you cant just message someone and then block them. its just one of the many flaws with the block/swear filter/pm settings,