In my universe there's a technology called Digistruct. It's a lot like the theory of solid light. Instead of creating an incorporeal copy of an image that can be interacted with, such as a hologram, we are actually able to create full copies of all sorts of things from blueprints. It was how I summoned Deathtrap, his blueprints are programmed into my arm and I could digistruct him at will. It was all based on ancient alien tech, a culture called the Eridians. We could even digistruct people in case of accidental death or dismemberment. Handy really. Seriously they like steal your money though. Probably better than being dead.
Anyway my point is, the tesseract shares a lot in common with the whole digistruct thing. People who have left seem to be able to come back but not remember anything. And I have to imagine that our universes aren't being changed at all by us existing here. Certainly isn't showing up in the mediums we apparently come from although that would be BOSS!
So my theory is that we're all just copies. The tesseract somehow manages to get DNA scans in our universes and can reconstruct us here. People who are scanned in their world and cannot be fully reconstructed here have their blueprints altered in order to function within the constructs of this universe.
Too bad it can't be used as an excuse here. "Sorry officer, since I'm not actually real I'm just a copy I can't be held liable for destroying that car. Even though it was ugly and totally deserved it."
As for why my digistruct tech doesn't seem to work here, I'm guessing it's cause the tesseract doesn't want me building up competition. Or maybe its version of the reconstruct process fucked it up somehow.