So, this is becoming more of a problem with people waiting in Revenant's Toll for the expansion: spammers of all types, freely filling your chat log with anything, and you can't do anything about it because of the obscenely long loading times.
I know they want to prevent you from doing anything but typing during any conversation with any NPC, any loading screen, any cut scene, etc., but I would sincerely enjoy it if you could blacklist people before this happens:


Am I alone in this? I mentioned it in /shout after and some people were really pro-spam, it seems.