The fast-food chain is extending a compelling but unfruitful promotional campaign.Investors may recall McDonald's (MCD -0.59%) second-quarter results weren't exactly thrilling. The fast-food chain missed revenue estimates, in addition to falling short of its earnings estimates. Indeed, same-store sales fell here and abroad, with the domestic slump being the first one since COVID-19-crimped 2020. As CEO Chris Kempczinski explained during the quarter's earnings conference call, "Beginning last year we warned ...