Unexpected behavior of middle-click on UNIX (X selection pasting vs. moving the cursor)

[smortex]

The Xorg selection mechanism is currently broken with monod: when a middle-click occurs, the caret is moved at the cursor position and nothing more happens (same as a left click).

I would expect the current X selection to be pasted at the cursor location, and the caret not to move.

Tested on FreeBSD with Firefox 50.1.0.