By "Type-1 Metagaming" I am referring to making decisions in a current game based on events that happened outside the game previously (this could mean events in a previous game, or outside Mafia entirely; whether the distinction matters is perhaps worth discussing later). This is opposed to "Type-2", which is making decisions in a current game in order to affect future games.
I'll start with Aliases, and maybe work my way through the alphabet (probably not, I am just unreasonably amused by "The A to Z of Type-1 Metagaming").
It is common in Mafia to compare a player's behavior in a current game to their behavior in past games, in order to help deterimine that player's alignment. It is not so common (though by no means unheard of) for players with an extensive track record (good or bad) to play games under an alias. This can be for a variety of reasons, but one result is the other players can not use the Metagame against them in this way. Is this an unfair or unethical advantage?
(Note: This should not be confused with the practice running games