Quote from peteroupc »Review C.R. 800.4e: "If combat damage would be assigned to a player who has left the game, that damage isn't assigned." Thus, Puresteel Paladin doesn't assign combat damage to that player (review C.R. 510.1). And since no combat damage has been assigned this way, it isn't dealt either (under C.R. 510.2, only "combat damage that's been assigned is dealt"). And since no combat damage has therefore been dealt to a player, Sword of Feast and Famine's triggered ability doesn't trigger (C.R. 603.2).
Quote from peteroupc »It appears that a Puresteel Paladin is attacking a player, then that player concedes the game. This makes that player leave the game (C.R. 104.3a). However, even though Puresteel Paladin is still attacking that player (C.R. 506.4), it doesn't assign (and thus deal) combat damage to that player (C.R. 800.4e, 510.2); thus, Sword of Feast and Famine's triggered ability (or any other ability of the form "Whenever equipped creature deals combat damage to a player...") should not have triggered here.