2016-01-22 : Any abilities that trigger while Remorseless Punishment is resolving will be put on the stack after it has completely resolved.

2016-01-22 : No player may take any actions between the two times the player goes through the process.

2016-01-22 : The player can’t choose to discard two cards unless they have at least two cards in hand. Similarly, that player can’t choose to sacrifice a creature or planeswalker unless they control one. This means that if the target opponent doesn’t have two cards in hand and doesn’t control a creature or planeswalker, that player will lose 5 life and then lose 5 life again.

2016-04-08 : The same player chooses both times. In a multiplayer game, you can’t choose a different opponent to repeat the process.