According to Section 3(a)(1)(A) of the Creative Commons BY-SA 4.0 license, you need to retain the name of the creator when sharing licensed material.
If You Share the Licensed Material (including in modified form), You must:
A. retain the following if it is supplied by the Licensor with the Licensed Material:
i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);
Deleting an account dissociates the user's pseudonym from their content against their will. The question no longer displays the creator's name in the main UI or in the edit log.