I did a quick search, didn't immediately see this one posted:

The player character("Nomad"), will sometimes speak lines in a different voice, with the audio originating from the player character, and the lip sync running on that model.

This can happen with entire lines(I've seen it twice getting congratulated at rally points for taking someone down), or partial dialog(seen it a number of times where I grab a guy, and he curses at me from his model, then the next line(something like "ok, ok!") is spoken from and displayed on the player model).