Apparently it's only possible to block a specific user that is logged into a spectrum user list, however when a user isn't online in a Spectrum chat or on the friends list which gives you user management options, it is not. The default website profile page does not have user management options at all. When a specific user isn't online you would need a mutual friend request first to be able to block someone. The standard search functionality only gives a message history with links to those messages in chats. I'm curious what the workaround for this when there is one. Jet