(I asked this question in Mathematics Meta around 3 1/2 years ago, but there has been no response.)
While browsing old questions in Mathematics Meta, I came across a user with an undeleted meta user account but with a (seemingly) non-existent main user account. I was under the impression that the creation of a meta user account requires the existence of a main user account. This implies that the main user account was deleted after the meta user account was created.
When a main user account is deleted, then shouldn't the associated meta user account also be deleted?