"Dreamwidth layouts seem to take it for granted that no-one uses icons for the sake of helping other people identify them."

That explains it. I was disoriented to find all the icons on the right, not only dissociated from usernames but where I don't see/process them until after I've tried to start reading the post. I have been recognizing people at a glance by their icons, but was only semiconscious of the process until it was yanked out from under me.