Over on his blog, Jeff Parker has some interesting thoughts on the difference between stories that are in continuity and stories that are “canon”:
While I consider our XFC stories in continuity, I don’t think I can decide what’s CANON. I think these are all modern heroic legends that will be added to and subtracted from, and what actually determines canon if anything, is the staying power of the parts generations of readers keep liking. Miller and Mazzucelli in Batman: Year One add in a bit with young Bruce falling into the cave and later the bat smashing through his window. Everyone liked that, so it got incorporated into later books and cartoons, and now it’s canon. Oh, and those pearls.
Earlier example going back to the Arthurian tales (they’re always my prime example relating to iconic characters)- Gawain was for years Arthur’s number 2 knight, but as the stories pass through France, Sir Lancelot gets added into the mix and eventually supplants that role because people like the story arc with the Guinivere triangle. Modern superhero comics correspond easily to the Arthurian tales- we even try to write the eventual deaths of our fictional heroes because we have a need for them to have that linear arc.
The publisher or a specific group of fans can try to nail something down, but it’s time and the collective of readers who will determine what part of the legend stays. So there’s no need for us to get too bent out of shape when a development we don’t like happens, we just have to count what we like. Future creators will simply diminish the importance of that event or forget it altogether unless it has real staying power.