I do find this to be a rather scummy move. Much like when you swing at the open player with a small
lifelink creature, or one with a card draw trigger. It's a reward for the accomplishment. You've made that play for the reward. Scooping prior to the damage is just spiteful.
Many times when that has happened to me, I was relying on those resources to deal with my remaining two opponents. Suddenly I've been denied those resources, but player 1 is still out of the game. Since I didn't gain my advantage, the board now grinds to a halt with the other three players. Player 1 is now moping around and griping that we haven't ended the game yet. And I just say, "well
SOMEBODY denied me all those resources a while back." A Karmic consolation prize.
My personal code of conduct is that I do not concede in a multiplayer match. It is fun when I am able to
defeat all my opponents. I assume that others find a joyful sense of completion in this as well.
One exception is when the entire table scoops. Like when Player A casts a
Torment of Hailfire for a bazillion. The remaining players all talk amongst ourselves. "I can't
stop that." "I can't
recover from that." "Let's just say he wins." ok. Game over. You win. Let's all shuffle up and play again.
I would actually like to see a new entry in the comprehensive rules that would make it so that in a multiplayer setting if a player concedes the game, that it does not
deprive any of the remaining players from any resources or triggers that they may have gotten as a result of combat with that player or as a result of moving through the phases of that players turn. Something to that effect to
negate spite scooping. While also allowing for Timmy to leave the game immediately when his mother calls.