How do I delete my account, and what happens to my posts?

Account deletion is handled in your account settings, not in the forum.

When an account is deleted, the forum member record is tombstoned rather
than removed: your identity, display name and IP addresses are erased, and
your posts are re-attributed to a "deleted member" placeholder. By default
the text of your posts is kept so that threads other people are relying on
stay readable; you can ask for it to be removed instead.

Records of moderation actions are kept, with your identity reduced to an
identifier nobody can trace back to you.