Last time we discussed the history of Marvel and DC's respective Universes, and the broad outlines of just how these storytelling mechanisms came to operate. This isn't a new story - for anyone whose familiarity with superhero books goes back longer than a few years, this is familiar territory, practically Stations of the Cross for nerds.
But it should be repeated, for the benefit of those who may have come in late, that the differences between Marvel and DC have always been momentous. Or rather, they have always seemed momentous. If you grew up reading comics anytime between 1961 and now, you were probably either a Marvel fan or a DC fan. Now, of course, it goes without saying that most people who read superhero books are both, because retaining that kind of kneejerk corporate allegiance into adulthood seems problematic, at best. But regardless of what you read now, when you were a kid you probably loved one more than another. It depended on what struck the deepest chord with you at the youngest age. For me, I was a dyed-in-the-wool Marvel fan from the beginning. When I got into superhero books, there were a few years where I didn't touch anything that wasn't Marvel. Now, it wasn't long before I "broadened my horizons", if you consider buying Superman alongside Spider-Man to be an exercise in expanded consciousness. But even if I liked a lot of DC books, I was still on some deep, cellular level a Marvel fan - I was imprinted on Stan Lee like a little baby bird on his mother.
It's hard to keep bias from butting in. A Marvel fan, looking in on the DC line, might see books like All-Star Squadron and Infinity, Inc. and the original Crisis as comically dense, convoluted and just plain odd. (Just now I glanced at the Wikipedia page for Earth 2 and saw that Earth 2's Quebec was an independent country. What the fuck?) Conversely, hardcore DC fans loved their multiverse, and loved all the stories that explored and defined all the little nooks and crannies and mysteries thereof. As many have noted, despite Marvel's seeming insistence on heightened continuity between their titles - dating back from the very early days of the post-1961 MU - the supposed fetish for continuity was more accurately a fetish for consistency. The two concepts are similar and related but not synonymous. The multiverse as it evolved at DC was an instrument of continuity, designed to circumvent contradiction within a rather cumbersome metafictional mechanism. The multiverse as it was utilized didn't really allow for a more ginger sense of consistency, like that at Marvel - it was all or nothing. if you had different worlds devoted to different versions of the same characters separated only by a few decades, well, by gum, you kind of had to follow that logic to its natural conclusions.
Continuity, as it has come to be understood in the context of these ongoing serial shared-universe adventures, is a dogged and inflexible devotion to absolute fidelity between all extant elements in a given context. In modern fandom, it has taken on a pejorative association - as in, the only people who care about "continuity" can't see the forest for the trees, etc etc. Consistency is less about exacting detail and more about broad strokes. This does not mean that a consistent system cannot also rely on tight continuity when it serves the purpose of the story. But the operative phrase is "when it serves the purpose of the story": if it doesn't serve the purpose of the story, or of future stories, it can easily be abandoned.
A few examples come to mind without effort. In the late 90s, after the character had been soiled almost beyond recognition by a progression of increasingly pitiful stories over the previous half-decade, the fledgling Marvel Knights imprint attempted to relaunch the Punisher as a mystical warrior, fighting demons and angels with magical guns. This relaunch failed so badly that the next Punisher relaunch, courtesy of Garth Ennis and Steve Dillon, didn't even bother to explain how the previous story had been swept under the rug. The events of the previous series were dismissed with a single cryptic remark in a narrative caption. No one really cared because the magic-themed storyline had been so unpopular. The Ennis / Dillon run single-handedly rehabilitated the character and restored him to his place of prominence in the company's pantheon.
Similarly, Iron Man was so badly misused in the mid-90s that drastic measures were necessary to restore the character to his previous status quo. In the space of a year he had been turned into a murderer and a betrayer - revealed as Kang's double agent in the Avengers since the very inception of the team - and subsequently replaced by an alternate-universe teen version. Thankfully, Onslaught and Heroes Reborn enabled this chapter in the character's history to be unceremoniously closed. When Iron Man returned a year later as part of Heroes Return, he was the old Tony Stark everyone knew and loved. Kurt Busiek didn't waste a lot of time explaining the hows and whys of the retcon, it just was. Finally, in an annual backup somewhere down the line, it was explained the Tony Stark had been restored to his previous state of grace because that was the way young Franklin Richards had remembered him when he restored the Avengers and Fantastic Four in the pages of Heroes Reborn. It didn't make a lick of sense and was, in fact, the comic book equivalent of waving your hands real fast and hoping no one notices. But people wanted so badly to forget all those horrible stories of the last few years that they willingly accepted the premise, and the fact that Tony was working as a spy for the Avengers' greatest enemy for over thirty years has never been mentioned again.
In contrast to these examples, I offer Donna Troy. Those who know how and why Wonder Girl came to be will know exactly how this DC example contrasts with the previous Marvel anecdotes. If you cut yourself, you need to get stitches and cover up the gash with a bandage. The only way to let it heal is to leave it alone, which usually means being very careful so as not to open the stitches. If the cut is big enough you are still left with a scar, but nowhere near as massive a scar as you can get from picking at the stitches, getting the gash infected, and pulling at the scabs. If the magical Punisher represents the bad cut that nonetheless healed well enough that you can barely see the small scar that remains, then Donna Troy is the huge gash that eventually needed surgery to remove gangrenous lesions, which resulted in almost losing the leg due to osteomyelitis and having to endure months of painful physical therapy as a result.