If someone takes the translator chip... no, there wouldn't be much point (while in armor, that is). But so far, no ones has. And just because your character might not use it, doesn't mean they don't know how.

And yes, your voice would sound different, as it would be your suit's main AI voice doing the speaking. So that could be less persuasive... just depends on the audience, the AI, and the situation. But there is certainly something to be said for someone interrogating you in your own tongue.