There is a massive issue that isn't addressed at all, but is incredibly important, I feel.
If I buy Moby Dick, and can't understand it because I'm a shitty reader or not interested in something like "theming" and "metaphors," I have several options. The option most analogous to an "easy mode" is just reading the Cliff Notes summary of Moby Dick. Sure, it'll explain the metaphors and themes, but it is missing, you know, the READING (Edit: for enjoyment) part. The option most like what Dark Souls has is: Learn to read first, then come back.
In Dark Souls, what actually happens is that you're required to respect the game before it will respect you. You must learn its rules, how to play it the way IT wants. This is, I think, a good thing to have in some amount. At the very least, we are in desperate need of games that teach you as you play.
Even HAVING an Easy Mode option will likely have negative effects. Many reviewers, not understanding that "despair" and "hopelessness" are two of the most important concepts pushed by Dark Souls, will bust through the Easy Mode in no time at all and never actually learn. They will condemn the game for reasons that simply wouldn't exist when playing on its intended difficulty. There SHOULD be a barrier to keep out "casuals" that only want to push a button and see pretty lights, because that's leaving out all the vital parts that makes Dark Souls so thrilling.
Considering that the majority of the satisfaction of Dark Souls is from the journey and the learning, and especially the overcoming, an easy mode just can't work for that sort of game.
Here's another analogy. Imagine, two miles away, there is a crate full of cash. The Dark Souls method: Run, pussy. The alternative method: Well, you can run, or you can take this moped. Your choice.
It's immediately apparent how much more satisfaction you will have when you run the gauntlet over the moped option, but what is less apparent is the fact that even providing an option will make many people forsake satisfaction just to have easy rewards. This ties back in with Moby Dick. If I ever end up reading a novel like that in the future, I will read it in vanilla English, pausing only to look up definitions, the way it was intended to be read. Reading a Cliff Notes version might count as "reading the book" to a teacher, but it isn't nearly as fun and doesn't require any effort.
This is one of the longest posts I've made in some time, and possibly the longest one that isn't a response to someone else, so I apologize if it jumps around or doesn't fully explain certain bits that I may at first think are self-apparent.