Skype messages

Yeah, seems like it is.

When you remove someone from your contacts, both of you don’t see the conversation history and online status. You can accept them later at any time.

When you block someone, you get a notification that you blocked them, but they don’t — your status is always offline to them, but they often get a notification when you go online, if they didn’t unfriend you. You can’t send or receive messages from them, but they can still send you messages, pending unblock. You can’t see if they’re online or not. Although not required, you may choose to remove them from your contacts.

No idea if unblocking or re-adding to contacts will restore the chat history, but I would doubt it.