When the triggered abilities of Firebender Ascension are placed on the stack, it is impossible to determine which original ability caused each individual trigger.

Steps to reproduce

• Have the setting enabled that allows you to choose the order in which triggered abilities are put onto the stack.
• Control multiple creatures that have abilities which trigger when they attack, along with Firebender Ascension.
• Attack with those creatures.
• Put the creatures’ attack-triggered abilities onto the stack.
• A screen opens allowing you to choose the order in which the Firebender Ascension triggers—triggered by those creatures’ abilities triggering—are put onto the stack.

At this point, multiple Firebender Ascension abilities are placed onto the stack, but you cannot check which creature ability each of them originated from — that is, which ability will be copied when the Firebender Ascension ability resolves.
When putting the Firebender Ascension abilities onto the stack, only the creature ability that is on the top of the stack is displayed.
When you hover the cursor over a Firebender Ascension trigger, the original creature ability is highlighted, but in reality you can only confirm whether it corresponds to the creature ability currently on the top of the stack.
If three or more creature abilities have triggered, it becomes impossible to determine which Firebender Ascension trigger corresponds to any creature ability below the top of the stack.

As a result, the ability you intend to copy may not be the one that actually gets copied, which can affect gameplay.