Is the argument that the Prophet's prohibition (peace be upon him) against touching the ankles applies specifically to the izar (lower garment) and not to the thobe (upper garment) correct? And is there a violation of the Sunnah in making the thobe slightly shorter than the trousers such that the trousers show from underneath, if one does not specifically intend to make this a Sunnah?

Scholars have agreed that letting a garment hang low (isbal) is forbidden for a qamis (shirt/tunic) just as it is forbidden for an izar (lower garment), citing prophetic hadiths as evidence. Whatever part of the garment extends below the ankles is unlawful and considered among the major sins. As for shortening the garment, what is permissible is that which falls between mid-calf and the ankles. It is disliked to shorten or lengthen clothing without need, just as it is disliked to deviate from the customary dress of the people of a land without a valid excuse.