Add comment for boat position broadcast

src/Entities/Boat.cpp

@@ -42,6 +42,9 @@ void cBoat::SpawnOn(cClientHandle & a_ClientHandle)
 
 void cBoat::BroadcastMovementUpdate(const cClientHandle * a_Exclude)
 {
+	// Cannot use super::BroadcastMovementUpdate here, broadcasting position when not
+	// expected by the client breaks things. See https://github.com/cuberite/cuberite/pull/4488
+
 	// Process packet sending every two ticks
 	if (GetWorld()->GetWorldAge() % 2 != 0)
 	{