Well, this was unexpected. I’m agree with Rama that this was an Epics’ decision based from business point of view and not the actual reasons indicated in the post. As some pointed out technical security issues would be easy to overcome for a company of this scale, and there are work-arounds that would completely eliminate them, unless it’s business security they’re concerned with. 
My speculation is this has to do something with the fact that Epic promoting their own educational channels and projects. And having a free growing wiki community may decrease the popularity and usefulness of such.
Again, Epic Games is a huge company and this bad play most probably was coming from their Education and\or Community departments, and I hope the core people leading developing of the engine and main business model will stay close to the original idea of openness and community focused development.
Love to all.