What is the validity of citing the action of Imam Malik—represented by his walking barefoot in Medina out of reverence for the Prophet, may Allah bless him and grant him peace—to permit the innovation of actions for the purpose of revering the Prophet, despite the Prophet having forbidden constant celebration and only commanded it occasionally?

There is no evidence that Imam Malik used to walk barefoot in Madinah; rather, there is information that contradicts this, as scholarly works mention that he used to change his sandals on Fridays. Furthermore, scholars who wrote about his virtues did not mention this; instead, they discussed his statement that he felt shy to ride a mount in the city where the body of the Messenger of Allah, peace and blessings be upon him, rested. If the report of him walking barefoot were true, it would have been mentioned in this context. The Prophet, peace and blessings be upon him, and his companions used to walk in Madinah wearing sandals. The report of Malik walking barefoot has no authentic chain of transmission and is not part of the Sunnah (definition).