Enable "showdead" in your profile. You can then view posts by banned accounts as well as posts that have been killed.
No they don't, they just ban people. Maybe they used to, but it's an unpopular method.
A HN ban is a shadowban. The user doesn't know he is banned unless being told, and he can post normally. You can, however, see all dead posts by enabling showdead option in your HN settings. I encourage everybody to do that. There are extremely few spam posts, most dead posts are dead for different reasons. Often I see people having been shadowbanned for years.