To be clear: we don't know that this change was made in post.

We do know:

• Achilles does appear in the original written Odyssey as a shade who speaks to Odysseus in the underworld

• Achilles does not appear in Nolan's film adaptation

• Sinon does not appear in the original written Odyssey

• Sinon does appear in Nolan's film adaptation as a shade who speaks to Odysseus in the underworld

So however they try to spin or frame it, it does appear that Ellen Page's character, Sinon, has functionally replaced Achilles in this movie.

Also, a ton of people are "dunking" on the haters by pointing out that Achilles was dead at the time of the Odyssey. Imagine being so retarded that you 1) can't simply look up whether or not Achilles was in the Odyssey 2) can't fathom how a dead man might appear in a mythological story that includes a trip to the literal afterlife. I'm assuming most of these dipshits are operating in bad faith, but some of them (based on their headshots) appear genuinely stupid.