I would argue that Harry Potter's scar isn't so much defined in terms of being a "physical imperfection"—rather, it is important for the ways in which it serves as a connection between Harry Potter and Voldemort. Within his universe, Harry Potter is famous within the wizarding community for his role in the downfall of Voldemort and for being the only person to survive the Killing Curse. The scar is in part a symbol of this, representing his status as it relates to Voldemort.
As the books proceed, the scar's role in representing Harry's connection with Voldemort will further intensify as we find out the degree to which the two are truly linked together. The scar is more than just symbolic: it exists as a very real bridge between Harry's mind and Voldemort's. Again, the physical scarring is entirely subordinate to this connection that defines it.