Multiple Replacement effects

[pyr0ma5ta]

Bonus: I read in an article recently that there has been a change to the way replacement effects are applied if more than 1 is relevant.  Is this true?  Something about Pyromancer's Swath + Furnace of Rath + Lightning Bolt to the face dealing only 8 rather than 10.  First, is this actually a change, and second, what is the relevant rule?

Thank you, oh mighty rules gurus, in advance.

I removed the question you answered yourself, and changed the topic to match the remaining question.  In the future, if you have two completely seperate questions on completely seperate topics, make two seperate posts, please.

  -- Clariax

[Clariax]

There is no change in this interaction.  As for whether it deals 8 or 10, that's a decision made by the player taking the damage (they'll likely choose only 8).  When multiple replacement effects attempt to replace the same event, the affected player (guy taking the damage here) or controller of the affected object(s) chooses which to apply first, and then if the other is still applicable to the now replaced event, they will still be applied afterward.

With Lightning Bolt, Pyromancer's Swath, and Furnace of Rath (Please include oracle texts in the future)...

|Instant| Lightning Bolt deals 3 damage to target creature or player.

|Enchantment| If an instant or sorcery source you control would deal damage to a creature or player, it deals that much damage plus 2 to that creature or player instead. / At end of turn, discard your hand.

|Enchantment| If a source would deal damage to a creature or player, it deals double that damage to that creature or player instead.

... Lightning Bolt's effect deals 3 damage.  Both Furnace and Swath attempt ot replace this event.  The player taking damage may choose which to apply first.  If he applies Swath First, the event is now "5 damage," which Furnace then replaces with "10 damage."  If he applies Furnace first, the event becomes "6 damage," which Swath replaces with "8 damage."

419.9a. If two or more replacement or prevention effects are attempting to modify the way an event affects an object or player, the affected object's controller (or its owner if it has no controller) or the affected player chooses one to apply. Then the other effect applies if it is still appropriate. If one or more of the applicable replacement effects is a self-replacement effect (see rule 419.6d), that effect is applied before any other replacement effects. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 103.4).

[Jacob Orlove]

Is there a specific reason why this works differently from triggered abilities?

[Clariax]

Is there a specific reason why this works differently from triggered abilities?

The simple answer is "because the rules say so."

Replacement effects in general work rather differently than triggered abilities.  1) they're effects, not abilities (pretty obvious by the names, yes, but many people miss this difference).  2) There's no using the stack involved in applying replacement effects (goes back to point 1, they're not abilities, but effects).  3) Replacement effects themselves don't have controllers.  The spells/abilities that created them might, but an effect itself has no controller.