Transfer Post and Reply ownership to Admin when Employee leaves company

From time to time, an employee who has contributed the best answers, posts, and replies leaves the company. If I ban, we keep the poster's name, but if I delete it, it goes to anonymous. This leads to second-guessing whether the answer is valid or the source of the answer.

I would like to transfer the author of the post and replies to admin or an employee anonymous account (with a non anonymous name) in order to keep the impression of the validity of the answer intact.