Since the content on PSE is licensed under CC BY-SA $4.0$, I suppose the content that is once posted on PSE becomes part the free culture (correct me if I am wrong), and thus, even if the author decides to delete a post of theirs, the community can still decide to keep the content of the post up (of course, without linking it to their name if that's what they wish). Currently, a no-delete policy only applies to accepted answers, however, I think it'd be a good policy to adopt for all posts (or at least, for all posts with a positive score). As I already mention, I think the user should be allowed to disassociate their name from the post if they wish to do so (it would still be visible in the edit history, I suppose).
I was led to this idea due to a recent social media post by an SE user who expressed that they plan to delete as much of their content as possible from one of the SE sites because they were disgruntled by a moderation decision made on the relevant SE site regarding one of their posts. The anecdote is not of any particular interest except to drive home the point that we wouldn't like to lose valuable content if a user gets angry at SE (for whatever reason, justifiable or otherwise). And, due to the CC license, I think we have the ability to make sure we don't lose the content in such cases.
I suspect that this would be an SE wide policy but I suppose it is a good idea to discuss it within the PSE community first. If this is not the right approach towards discussing an SE wide policy, I'd be happy to delete this post and post it on SE wide meta.