I guess in combination with the 'can't stop it' twist that would mean that you can't stop talking in these old and random languages. So people will think you're crazy and you'll end up in some kind of mental illness hospital.
How is that different from 'being able to fly' or 'being able to turn invisible'? My understanding of OP's twist is that you don't have full control over your ability but that the skill is permanently active.