It's also set in the future, so I like to think of it as transcendent rather than unrealistic. Records are being broken all the time (look at Usain Bolt and Michael Phelps). Who is to say that by the time the government takes over to that extent, more refined training methodologies and pure determination won't result in traceurs that would appear superhuman to today's athletes? Faith doesn't do anything really that impossible. It's just higher and farther, faster and harder than we can hope to perform at the moment. That's one of the things I like about the game; it's just a couple of steps out there, and the possibilities of those steps are enticing and not too far away to discourage.

There's a video on that list that analyzes the first trailer for Mirror's Edge, and they mention something about how some guards have "PK" on their uniforms, and others have something else.  I noticed that the first time I watched any of the trailers as well, and I think it might just be a neat little nod to the community.