X clipboard The X window system has its own clipboard. It is also known as a cutbuffer. Any text or content you mark by highlighting with the mouse cursor is automatically copied to this clipboard. This is known as the PRIMARY selection or X Window selection or just selection in X jargon. When you middle-click the mouse cursor at the destination location, this copied content is pasted there.

In 13.10, Shift+Insert pastes from the selection buffer (the thing that selecting text writes to). In Libre Office, Chrome, and Firefox, Shift+Insert pastes from the clipboard. I would thus like to configure gnome-terminal to do the same.

While this isn't a solution, hopefully this explanation will make it clear WHY. In Ubuntu there are two clipboards at work. One, which everyone is familiar with, the freedesktop.org clipboard (captures Ctrl+C command) The second is a clipboard manager that has been at play since before Ubuntu even existed - X11. The X Server (X11) manages three other clipboards: Primary Selection, Secondary Selection, and Clipboard. When you select text with your pointer it gets copied to a buffer in the XServer, the Primary Selection, and awaits pasting by means of the Mouse 3 button. The other two were designed to be used by other applications in a means to share a common clipboard between applications. In this case the freedesktop.org clipboard manager in Ubuntu already does this for us.