Technically, they could retain posts from users if they are irreversibly anonymized. However, ensuring with 100% certainty that none of your posts ever contained any personal data that could lead to the identification of you as an individual is challenging. The safest option is therefore to also delete your posts.

It’s definitely not bad, it has some features discord is still missing. But if you looking for an alternative it’s for sure the thing to check out! Also it is opensource which is quite neat! https://github.com/orgs/revoltchat/repositories