In a previous thread, Smithereens expressed concerns over people editing their posts during a mafia game in order to conceal any mistakes they may have made. After reading the thread, I now feel I need to express concern over people deleting their posts during a mafia game.
I would recommend something similar to the case with people editing posts. My idea is that, when a post is deleted, the block the post was in remains there, and it still has the username and profile picture of the person who posted and deleted it, along with text saying "this post has been deleted", and an icon (much like the 'edited' pencil icon).
The purpose of a deleted icon along with the text is so that people can't actually make it look like they've deleted a post by typing "post has been deleted".