Looks like he just decided to purge his own account via the option in settings:

https://communities.win/settings?type=purge

I think when admins delete an account it says something like “this user has been suspended”, and when a user deletes their own account it says “this user has deleted their account” - which is like a purge but the account is closed after and can’t post any more. The OP of that thread you linked can still post, he just purged his whole history for some reason