@IceWolf until you try to copy something
@yeah Shift-click! :3
[And make sure your pane is the width of the terminal, e.g. by maximizing it. That gets rid of the extra spaces on the right.]
@IceWolf shift+click doesn't do anything
@yeah Well shift-click-and-drag, to bypass tmux's mouse support.
[This is dependent on the terminal emulator, but every one I've tried does this.]