As far as monetization goes, we plan to add premium features like stickers, and voice changers. There will be people who do not want to talk with their voice precisely for the reason you mentioned: one can consider it to be a sensitive data. Why do we want to offer voice-alteration as a paid feature? Because, if it is free for all, we fear that there will be people abusing the feature that jeopardizes the authenticity of the platform.
We do NOT plan to sell or share users' data with a third party, or use users' data to train an internal AI model because I think that fundamentally betrays the goodwill that users bring to our platform.