What is the "Anya bug"?

Those who have finished the game know that when you have rescued Anya in act 5, Malah gives you a Scroll of Resistance that "permanently" increases your resistances to the elements. But we also know that Malah did not make it past Firebolt casting 101. That shoddy little scroll does not work quite the way it is supposed to.
When the scroll is cast, it does increase your resistances. But when you die, that bonus is lost, even though it does is not displayed on the Lying Character Screen. The bonus is regained when you reenter the game, but for the rest of the game in which you died, your resists are really 10% lower for each Malah scroll you used - up to 30%. That is quite a difference. Your paladin may not have 90% resist all, maybe he has 60% all res.

This is of special concern to duelers, who often die multiple times in each game - and it also means that if you lose to an elemental attack once, you are likely to keep losing.

In turn, hardcore players don't have to worry about this bug at all, for obvious reasons.