Tradition
Oral tradition has been the most favoured method of recording history and telling stories, save for The World As I Know It. It is the main method of education for travelling Players, typically shared around a campfire and a hearty stew. However, as expected by the method, certain details over time have become embellished. There is no credible proof that Giants once roamed the Overworld, nor is there any confirmation that Nether reactors once existed. Of course, what modern historians fail to realise is that the Updates may just as well add new blocks, as it may remove them.
Though the causes of this tradition is unknown, a Player hitting their held weapon against their chest has become the equivalent of a thrown gauntlet. Upon reciprocation of the action, the duellists run off to find some official dueling grounds, or some other sanctioned arena. Special safeguards must be erected to prevent cheating and other shenanigans. In a battle between Players, there is no telling what may happen. More interestingly, the method to decline a duel offer is for a player to repeatedly crouch and uncrouch. This has since been adopted as a universal sign of peace, and way of greeting other Players.