I just received an email from the Sydney Opera House, "For most events there is no formal dress code although for safety reasons we do ask that patrons wear shoes at all times." Assuming I wear shoes with my argyle jacket, I think I will be ok. To be fair, the email further stated that most patrons dress in "smart casual wear" and that any special events may have information about dress code provided with the tickets or confirmation. I believe that I will proceed with the argyle jacket.