আপনি can block MESSAGES from them and আপনি can prevent them from posting on your দেওয়াল if আপনি aren't a অনুরাগী of them. I don't think আপনি can block them from seeing আপনি though. But,if he is stalking আপনি অথবা bothering আপনি then আপনি should tell one of the admins to get him banned/suspended অথবা even IP banned where he CAN'T make another account on the device he is using. (Unless he gets another one and goes through that.)