A very old idea of mine that I've never come to implement has been for an online forum to keep a record of all prior versions of an edited post.
I.e. you'd have a table with post_ids and another table where you have one entry for each version of the post.
In a view, you'd simply always display that as one table, of course (which would possibly make it backwards compatible with existing forum software).
To save some space, old versions of posts could simply be diffs from the latest version (or the first version, whichever you prefer).
No more deleting posts, only superseding them with new versions, admins & maybe privileged users like moderators always being able to see what you edited in or out.
Of course, that's totally against GDPR laws' "right to be forgotten"