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Describe the Bug:
Forsaken Wastes makes Mirror Universe's activation reduce everyone's life to the lowest player's, and Wall of Shards' cumulative upkeep cost is still payable.

Which card did behave improperly ?
Mirror Universe.

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
Post-BFZ, but it's extant in every version going back to at least the initial release of 3.0 in January 2012 (when it was still in assembly).

What exactly should be the correct behavior/interaction ?
Nothing.

Comp rules:
118.7. If an effect says that a player can't gain life, that player can't make an exchange such that the player's life total would become higher; in that case, the exchange won't happen. In addition, a cost that involves having that player gain life can't be paid, and a replacement effect that would replace a life gain event affecting that player won't do anything.

118.8. If an effect says that a player can't lose life, that player can't make an exchange such that the player's life total would become lower; in that case, the exchange won't happen. In addition, a cost that involves having that player pay life can't be paid.

Are any other cards possibly affected by this bug ?
None of the other exchange life work any better with any of the other can't gain life or can't lose life effects. They are, respectively:

• Cliffside Market,Magus of the Mirror, Mirror Universe, Psychic Transfer, Soul Conduit, Tree of Perdition, and Tree of Redemption.
• Atarka's Command, Erebos, God of the Dead, Everlasting Torment, Forsaken Wastes, Havoc Festival, Leyline of Punishment, Platinum Emperion, Skullcrack, Stigma Lasher, and Witch Hunt. (But not Flames of the Blood Hand or Sulfuric Vortex.)
  
• Just Platinum Emperion, I think?

Wall of Shards checks only for Platinum Emperion, but only for that specific card (even if it's lost its abilities, or some other card copied its abilities), but none of the other can't-gain-life effects.

Also, I note that Mirror Universe checks for the presence of Lich, which makes life[] lie about its controller's real life total; but

• None of the other life exchangers except Magus of the Mirror check for it.
• It assumes that Lich's controller's real life is exactly 0, despite Lich not replacing loss of life.
• It doesn't check for Platinum Angel and other can't-lose-the-game effects, which also make life[] lie.

Korath wrote:(But not Flames of the Blood Hand or Sulfuric Vortex.)

You mean those work as intended?

They're different wording, so the exchange should still happen (and not increase the life of the player with the lower amount); but they're approximated the same way as the others.

That's what I thought but what was confusing is that the same should be the case for Atarka's Command wording like "your opponents can't gain life" so when the exchange makes them loose life the exchange should happen.And the same goes for Stigma Lasher wording "that player can't gain life".

Rule 118.7 quoted in the original post says "can't gain life" effects entirely prevent life exchanges that cause that player to gain life. Which, no, doesn't make much intuitive sense.

The run-of-the-mill replacement effects on Flames of the Blood Hand and Sulfuric Vortex (and, for that matter, on Lich, Nefarious Lich, Tainted Remedy, Boon Reflection, Rhox Faithmender, and Alhammarret's Archive) allow the exchanges to happen, but change their effects: the player can still gain life, but what happens when he does is different.

Similarly, if some card had an ability that read "Gain 2 life: do something" or, more concretely in the case of Wall of Shards, "Cumulative upkeep: an opponent gains 1 life", Sulfuric Vortex would make those costs payable but have no effect (so you'd "do something" or your Wall of Shards would live for no effective cost), while Everlasting Torment prevents those costs from being paid (so you couldn't "do something" and your Wall of Shards would be sacrificed).

Which reminds me - Wall of Shards doesn't check for can't-gain-life effects either, except for Platinum Emperion. It should also fail in all the same cases exchanges of life totals do.

Korath wrote:Rule 118.7 quoted in the original post says "can't gain life" effects entirely prevent life exchanges that cause that player to gain life.

Yes,it entirely prevents the life exchange if thatplayer gainslife.What makes the difference is that player in contrast to "all players" or "players" which won't make a life exchange in any case since "that player" can't make a difference in those.And the cause "gain life" if the exchange doesn't cause that player to gain life but loose life the exchange happens.
that player in Atarka's Command is your opponent so if the life exchange makes the opponent loose life it will happen if it makes the opponent gain life it will not happen.
The same goes for Stigma Lasher "that player can't gain life" so when it damages that player = your opponent and the life exchange makes the opponent loose life it will happen if it makes the opponent gain life it will not happen.
The opposite will work for the above wordings for rule about loose life:
118.8. If an effect says that a player can't lose life, that player can't make an exchange such that the player's life total would become lower; in that case, the exchange won't happen. In addition, a cost that involves having that player pay life can't be paid.

Ah, I see the point you were making now. If player0 has 12 life and can't gain life, and player1 has 6 life but can, then yes, their life totals can be exchanged.

Ok, I made an HUGE effort and fixed everything your reported.
I also test the changes a bit and everything seems to work fine (thank god).

A lot of bugs have been fixed Gargaroz. but still there are issues in this gigantic post of bugs by Korath.
These have been fixed for the Exchange life totals vs. Can't gain life: Magus of the Mirror, Mirror Universe, Psychic Transfer, Soul Conduit.
(Cliffside Market hasn't been tested).
Atarka's Command, Erebos, God of the Dead, Everlasting Torment, Forsaken Wastes, Havoc Festival, Leyline of Punishment, Platinum Emperion, Skullcrack, Stigma Lasher, and Witch Hunt.

1- Still bugged are the Tree of Perdition, and Tree of Redemption. They do the exchange correctly if the player is going to loose life (with can't gain life effects) but still bugged if the player is going to gain life as their toughness still becomes as the life of the player, player's life doesn't change correctly so the exchange happens partly? The exchange shouldn't happen at all.

Korath wrote:Wall of Shards checks only for Platinum Emperion, but only for that specific card (even if it's lost its abilities, or some other card copied its abilities), but none of the other can't-gain-life effects.

Wall of Shards now works correctly with the other can't gain life effects also.
2- Wall of Shards is still bugged for the (even if it's lost its abilities) part.A Platinum Emperion enchanted with Darksteel Mutation still affects Wall of Shards.
This part or some other card copied its abilities)is fixed.

Korath wrote:Also, I note that Mirror Universe checks for the presence of Lich, which makes life[] lie about its controller's real life total; but

None of the other life exchangers except Magus of the Mirror check for it.
It assumes that Lich's controller's real life is exactly 0, despite Lich not replacing loss of life.
It doesn't check for Platinum Angel and other can't-lose-the-game effects, which also make life[] lie.

This has been fixed: None of the other life exchangers except Magus of the Mirror check for it.
3- This is still bugged: It assumes that Lich's controller's real life is exactly 0, despite Lich not replacing loss of life.
4- This is still bugged: It doesn't check for Platinum Angel and other can't-lose-the-game effects, which also make life[] lie.
5- Also Lich doesn't check if a your-life's-total-can't-change effect is in play - Platinum Emperion effect.