OS X still only supports Ctrl+V for paste in some places too.. Valve needs to do a better job of detecting platform stuff.
Same issue when activating a game through a code e.g. from a humble bundle: the code can be pasted using ctrl+v, but not the third mouse button.
To clarify, the steam widgets only seem to support interacting with the clipboard selection and not the primary selection. At a minimum, they should paste from the primary selection with a middle click.
I think shift + insert works, somebody can confirm?
Nothing extracted yet.
When Steam tells me that this is a new computer and that I should paste the security code received in an e-mail, pasting with ctrl-v works, however pasting with X11 text selection and third-button click does not.