Did you have a look at the documentation on how flagging works? What happens when you flag a post
Usually, one flag does not hide a post.
Though these settings can be adjusted according to the dynamics of the community by the admin. So it is the admin who decides how likely posts are hidden. The software offers settings to configure that.
User Reputation and Flag Priorities
When you or someone else deletes your post, it is soft-deleted, so staff still see that there is a hidden post and have the option to restore it.
Deleting a user is permanent. But there are other options like suspending or silencing the user