The user you are trying to block has already been blocked and hidden. Since you do not have the hideuser right, you cannot see or edit the user's block.
MediaWiki:Cant-see-hidden-user
From Cheng Hung Wen - Calligrapher and ART
The user you are trying to block has already been blocked and hidden. Since you do not have the hideuser right, you cannot see or edit the user's block.
