This a really fascinating analysis. When I completed the game I was torn between the twins and MPD hypotheses, but you’ve more or less convinced me that the latter is “right” answer.
Regarding the remaining obstacles to this theory, particular Eve and Hannah’s failure to really synchronise their dress, jewelry, etc., given your remarks about the original conception of the game explaining the contradictory lines, perhaps we can go further in considering how the evolution of the game’s concept might have affected the narrative. I think there may have been three significant stages:
The initial concept was the more traditional gameplay you mentioned: You play as a police officer who reviews interview footage, finds inconsistencies, and use it to build a case against the suspect.
At some point while developing the concept, Sam Barlow hits on an idea for a interesting twist: What if, instead of being one person, the suspect being interviewed is actually twins, pretending to be one person? The challenge for the player is to spot the subtle changes in dress and attitude that give this away.
Finally, after thinking about the concept and characters further, SB decides that instead of being actual twins, the two characters will be the same person, but with MPD that leads them to *believe* that they’re twins, thus adding another layer of psychological complexity to the story and the game.
Having written some fiction myself, I think type of structural evolution is quite common: You begin with the germ of an idea: A setting, situation or mechanic. Next you develop the plot, and things grow more complex and twisty, however only at a fairly surface level (many stories don’t progress further than this). Finally, you start to delve more deeply into the thoughts and motivations of the characters themselves, and you begin to shift the burden of complexity from the plot to the psychology and overarching themes.
If the game evolved this way, it might explain some of the oddities: They’re traces of the older concept still left behind. So the slip-ups and odd turns of phrase are from when the game way about identifying them, and the differences between Eve and Hannah are from when the “twins” theory was going to be the correct one.
Now, all of this might not be the way the concept evolved at all. It’s possible it sprung fully formed from the mind of SB one evening. But even so I’d argue that it does, at least, inform how the game’s story is presented to the player, and how they’re supposed to experience it. We’re at first encouraged to focus on the raw mechanics of the game: using the faux OS and video system, searching, watching videos, saving and tagging them, etc. Next we start to get into the meat of the plot, constructing a timeline of events, and noticing the obvious discrepancies between how Eve and Hannah act and dress. Finally we get past that and start to unravel the psychological mystery and explore the themes of fairy tales and identity.
So, we’re not supposed to solve the mystery right away, nor are we supposed to leap straight to the “right” conclusion. But leading us down the right path is difficult, especially when the order that we view the videos is semi-random. To that end, the script and the footage mighty deliberately make choices that encourage us in the right direction, even if they’re slightly in tension with the eventual solution. So, we can see how Eve and Hannah, even as a single person suffering from MPD, might have avoided tipping off the police by being more careful, but we can only see that in retrospect, because if they *had* been more careful, acting consistently in each interview, then there’d be no game at all. All we’d have would be footage of a woman whose husband was murdered, and who seemed to have a reasonable alibi.
Telling a story, particularly an interactive one, always involves some tension between strict realism, and deploying the kind of expositionary tropes that storytellers use to guide the audience in the right direction. In hindsight, the tropes can seem obvious, or silly and unlikely to the point of being plot holes. But that makes the mistake of believing a story is something that is only to be appreciated when it is 100% done, like a beautiful painting that we only see after the artist has finished with it.
In reality, storytellers need to write the story in front of an audience. A reader experiences a novel one word, sentence, paragraph and chapter at a time. If the novel only makes sense when you reach the final page, then you’ll turn off a lot of readers before you get there. So, you make some compromises, sacrifice a bit of realism here and there, in order to keep your readers involved in the story. The end result might be that the story isn’t quite as perfectly constructed as you’d like, but it’s a reasonable trade-off to make.