The "Try Avatar" button on the avatar detail view is disabled if it is shown via another user's "View avatar details" (QM) or "Avatar Details" (MM) button and if the user disables "Allow Avatar Cloning."
Even in this case, it is possible to try the Avatar by finding the avatar from the Avatar Marketplace list (or hopping avatar using "More From This Creator": open other and go back to the one). So it is meaningless to refer to the cloning switch (I guess this is just a bug, but I comment just in case).