Last week in MIA, as I walked up to the doorway as F boarding was announced, an elderly gentleman had gotten up and was sort of blocking my way. He looked at me and motioned that I should go ahead of him and his spouse. I refused and said, "no, sir, after you." Wouldn't you know, although the agent was on the PA right then announcing F boarding ONLY, there he was with his Group 5 BP. The agent politely told him - "Sir, we are boarding F right now, and you are in group 5." She might as well have been speaking Greek.