- last post: 01.01.0001 12:00 AM PDT
Okay...
The Covenant DO speak some English. This was shown in their first words to humans, in the declaration of war, "The Gods have willed your destruction and we are their instrument."
This struck a bit of horror into the humans because this act showed that the Covenant had been watching us for some time, and long enough to learn at least one of our languages.
Jacob Keyes is also an intelligent man. Not only does he have knowledge of how to pilot Covenant craft, as seen at the end of that chapter, but I'm sure he also understands a bit of the Covenant's language.
Anytime you've heard the Covenant speak English in the game, it's their own talent, not translated.