I am anyway in favor of distributing the data shared here under a strong copyleft license. A legal notice that every instance can include in their TOS. Data from users of this instance and all posts on this instance should then be open and any products that build on this data or use it anywhere must also publish it with the same license (AI, data brokers, …).

Together with the AGPL for the backend code, this could provide a robust framework against exploitation. Anything these companies do with the data would have to be made available for everyone, which could only be an enrichment for the general public.