Is wearing a white shirt to be signed by friends and colleagues before graduation, rendering it unusable later, considered a waste that is displeasing to Allah?

There is no doubt that clothing is respected property that must be protected from spoilage. Islamic law has forbidden squandering wealth, citing Allah's saying: ﴿And do not be extravagant. Indeed, He does not like those who are extravagant.﴾ [Al-A'raf/31], and His saying: ﴿Indeed, the extravagant are brothers of the devils.﴾ [Al-Isra/26-27], and the Prophet's (peace be upon him) saying: «Indeed, Allah disliked for you three things: gossiping, squandering wealth, and excessive questioning.»

Signing on a shirt removes its utility for wearing. In return, there is no significant benefit or interest in such signatures, which makes it a form of squandering and extravagance.

If it is assumed that there is a benefit to signing, it can be achieved by signing on a "notebook" or special "journals" that do not spoil the property.

A Muslim, in his actions, must weigh benefits against harms. If the harm is stronger, he should avoid it.

Therefore, signing on a shirt is a form of squandering wealth and extravagance, which is forbidden. There is no recognized benefit in it, and if there were, it could be achieved through other means that do not involve squandering and extravagance.