The guys over at the Halo Story Page were able to get Eric Nylund, author of Halo: The Fall of Reach and Halo: First Strike, as well as Eric Trautmann, the guy at Microsoft most closely connected to the Halo backstory, to sit still long enough to answer a few questions about the Halo storyline. Some of them are about small details and possible errors. The really interesting bits:

• The "artifact" found on Cote D'Azur that led the Covenant to Reach and Cortana to Halo is an "interesting little chunk of stone" according to Nylund, and contains multiple messages.
• As Trautmann hinted earlier, the answer to the question of who or what would wear a Halo-- already stumbled on by a forumgoer accidentally-- is important. The answer in general would seem to be angel, but what that means I can only guess.

Go take a look, the full article is quite worth it. Thanks Louis Wu at HBO.