The scenario: An enemy is atop a 499 foot cliff. A hero is at a place where he can stand and move freely (enough), let's say in the middle (around 250ft). Immediately after the hero's turn, the enemy will begin to fall straight down (past the hero and within his reach) for reasons unimportant.
Will a readied action to "Attack an enemy that falls within my reach" trigger?
I know that the RAI, RAF, and RACS answer is "Yea, of course". But RAW falling happens "instantly" (ish) for distances less than 500 feet (hence the restriction) and reactions happen after their triggers, unless otherwise specified by an ability.
Notes: No, the enemy is not using featherfall or any other fall-altering (faltering?) ability.