Bart's eye patch isn't for show, he lost his eye when trying to aid in the repairs to the Yggdrasil long before meeting Fei and Citan. Sigurd, his fellow comrade and retainer, saved him from greater harm, but also lost his other eye in the process. He personally customized his gear Brigandier, which he personally excavated himself alongside the Heimdal, to have a "patch" over the left camera. While this can't provide any advantage in combat, this would show his vanity and pride to spite his weakness. Despite his brash attitude, Bart is a kind-hearted guy who has deep leadership talents, and has an eye to survival with honor and dignity. He also pilots the Omnigear Andvari, which was excavated from Ft. Jasper and initially stolen by Shakhan.