Where does the idea come from that not allowing users to delete content is against the law/GPDR? You have the right to ask for deletion of personal information they store, and even that has certain limits. You don't have the right to force the company to delete content unless they granted you that right via the licence somehow. Whether this is a good or bad idea for a company to do is a different question. But I don'…
I suppose this would constitute indirect identification of a data subject under GDPR?