Zanallen wrote...
If we want to call this a retcon (It really isn't, but whatever), then Flemeth being alive is also a retcon. We made a choice to kill her in DA:O, but she was brought back in DA2. Her resurrection was explained (Basically, "magic"). Now, Gaider has said that Leliana's survival has an explanation, but it hasn't been revealed to us yet.
You´re wrong. In DAO, after you kill Flemeth you can tell Morrigan what you did, and she will say that her mother is far from being dead. This is DAO (the same game where you kill Flemeth), telling you that even thought you killed her, she may not be dead. That is not retroactive continuity, the writers of DAO planned for it, and it wasn´t added later on another game or dlc, it was right there in the main game.
You want to know what Flemeth´s codex says after you kill her?
She was slain at Morrigan's behest. At least apparently...
Now compare to what the codex says when Leliana is killed
When The Warden corrupted and destroyed the Sacred Ashes of Andraste,
Leliana drew her weapon and was killed alongside the guardian.This is a retcon for several reasons: 1) it is established in DAO that Leliana died, there is no suggestion of something else happening. 2) The suggestion that she might not be dead comes from a later (in real world time) chapter, namely DA2. That is retroactive continuity, it means modifying past events in order to better fit the new narrative that you want to tell.
The Flemeth appearance in DA2 has nothing in common, it is merely provides a in-world explanation to something that was already established in DAO through Morrigan and through Flemeth´s own codex entry: that she was only apparently dead.
I´m fine with bioware doing a retcon if they believe it is necessary, but don´t deny and evade about it like it is some mark of shame. Just admit that you can´t plan for everything in advance, try to be more careful in the future, and move on.