Unable to Blacklist?

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Date & Time: 2:24 PM
Frequency: Recurring
World name: Cactuar
Character name: Berteaux Braumegain
Party or solo: Solo

I left a troll party with some immature players and attempted to blacklist one in order to prevent being grouped up with them again. But the message I got back was "Unable to blacklist friends. Please remove from friend list and try again."

Sure enough, upon checking, this person was not in my Friend List. And upon trying to send them a tell, I get the message "Unable to send /tell. That character is on another World server and not on your Friend List. Use Alt+R to reply to a Party Finder message."