I don't really understand why relationships with someone who quits require any sort of retcon... I mean relationships are wildly mutable things. I would have thought that in cases where it were possible to easily explain something in story, that would be the preferred approach. Character B quite the game? Alright.. then the relationship didn't work out, and there are a myriad of reasons why.Â
Retconning is the preserve of stories that are no longer plausible for whatever reason. If your character did A in their past, only for the player to discover that A was entirely impossible due to the game's lore (perhaps newly learned), then it may be possible to make a minor adjustment to the character by removing A from his past, or changing it in some way to make it plausible.
Just because something is inconvenient doens't mean that it should be written out, especially if it impacts other people's stories or interactions in some way. Better I would think, at that point, to consider writing a whole new character, rather than asking people to ignore an entire history of in-character interactions together.
Retconning is the preserve of stories that are no longer plausible for whatever reason. If your character did A in their past, only for the player to discover that A was entirely impossible due to the game's lore (perhaps newly learned), then it may be possible to make a minor adjustment to the character by removing A from his past, or changing it in some way to make it plausible.
Just because something is inconvenient doens't mean that it should be written out, especially if it impacts other people's stories or interactions in some way. Better I would think, at that point, to consider writing a whole new character, rather than asking people to ignore an entire history of in-character interactions together.