The Qestir

[Berethos]

Given the specificity of some of the Xaela tribe beliefs...I actually wouldn't put it past the Qestir to truly believe that it's just the spoken word that is the issue, and that it in written form (in whatever form is acceptable to them) is not an issue.

Do they eventually go silent as they grow up, understanding their parents culture?

It may again be a matter of specificity - sounds like grunts or babbles or crying may not be considered words and are thus acceptable, given the intentional nature of putting meaning into spoken words.

We can also see examples in the real world of what happens when someone grows up without being around those that can speak - they may be able to learn the words and understand them in terms of hearing them, but they actually display a great deal of trouble learning to actually speak them. I'd imagine that by the time they encounter those that can speak, they are past the point in their physical and cognitive development where vocal language development occurs, and so not speaking is actually second nature to them.