The argument of conciousness isn't really quite fitting here - I suppose GD is just about how huge and powerful the mind that it became from was. At some point this conciousness got so excessively powerful that it crumbled under its own strength - so omnipotent that it could not even grasp itself anymore. I thing this entity is so keen on eating whatever it finds because of the last thing that happened, last memory before the proccess was irreversible: I'm losing control. I need more strength. More resources.
And the zombielike thing the GD is, it is just following that last memory even when it doesn't make any sense. This also kinda reminds me of Transcendant, he also was subverted to a process that made his mind a such... thing. And it started to yield very, VERY strange stuff, with changing the universe to be as much alike his last memory as possible. Perhaps Great Darkness IS actually Transcendant, who somehow transferred himself to another universe and started consuming stuff until he became too huge and converted into GD. This would make for a very interesting plot right there.
I also need to point out that in BP's texts there is a mention of a Vasudan called Jester, he seems to have had a contact with or at least a view of the Great Darkness. That's probably why he is basically nuts/in need of lots of psychotic medicine.
@Soulrheever: What creepy thing? You mean in the empty void, or during Bosh's monologues?
Dead people? Genady and Kyrenmaten are dead, but Simms is only unconscious and Levi is actually only presumed dead. I mean, I think there wasn't a scene of him dying in Delenda Est, just charging at the enemy. If Tevs captured him, he might be prisoners of war (not really likely) or they may be using him for something related to MORPHEUS (more likely). The rest of that pack should be fine (Lopez depending on your choice in HFH), but presence of high-ranking Tevs in their midst is... puzzling.
I also would like to suggest that since Nagari is non-local in space, it might be also non-local in time, too. It isn't the first time when someone grabs an echo of dead people - either it's how Nagari works, non-locally in time, or this can be a kind of a remnant after a long gone mind, just like the Ancients. Or their minds are actually stored by something in the network for some reason. All three possibilities could be handy for extracting info thought to be long gone.
By asking about the "others", I rather meant people engineered in a way similar to Laporte - and with similar hidden goals to accomplish. I think Levi and Kyrenmaten would fit here (as replacements/complements to Laporte), but not Simms. While I wouldn't want to use non-canonical sources (Morrigan stories), I still think Simms is different in that regard to these two.
I've also found a thing that could be somehow related to Shambala. It could be hinted here
Since we've got quite some info on GD, I suppose couple of us theorists here should take a long walk back with that knowledge to the beginning of this puzzle, to look at things in another context, since there's a lot more information to use and search for hints.
I also wonder what exactly do these people in UT2 say - a shame but I don't really have the time to replay UT2 dozen more times or to manually search for text in mission files. By the way, is the hull integrity of Indus actually indicating the mental state of Laporte when you get to that segment of the mission? That would seem like a cool feature.