So a member required Account Deletion via the (Account Settings > Privacy and Security tab), which I accepted. However, although the user name is gone from posts he has made, an edit he made to one of these posts still shows "Edited x hours ago by..." and his name.

Is this intentional? If user data are deleted, why not the edit info?

It’s not the way the IPB software works. It’s always been like that. You can post a request in the feedback forum if you like for it to be considered to be changed. 

It would require a rebuild entirely, which is why those do not change. You will see the same with quotes. If a user has requested the account deletion and you have deleted the account, you have of course complied with their request

Thank you both.