It’s happened occasionally that a new user will wonder about the identity of a deleted user, whether, on the main meta or on a per-site meta (or indeed on one of the non-meta sites). Often such questions can theoretically be answered, either by simply have been around before the user was deleted, or by looking at contextual information.
Such questions might seem to go against one of the points of deleting a user, though: to dissociate them from all the content that they produced. They might make it easy for users to find the deleted user’s contributions in chat, for example. There might also be a privacy concern.
How should we deal with such questions? Not answer them? Close them as off-topic? Delete them?