Emmanuel, You are right and I overlooked the rights under for that queue for Privileged users.
On the other hand there is maybe a UI improvement to consider: If a user has no rights to create a ticket, you can still see the quick ticket creation dialog and the create ticket button, even if using them results in an error message since no queue is assigned. I would be cleaner to not present this dialog and button in the first place. Thanks, Thierry Discover RT's hidden secrets with RT Essentials from O'Reilly Media. Buy a copy at http://rtbook.bestpractical.com