Potential Methodologies for MUDs, at Game Studies. All my hot buttons, all at once. It's difficult to pick a single point out of this wide-ranging article on how to play and the players of MUDs, but the three aspects deserve a mention. Mortensen identifies three influences on how the game is player: the technical aspect (the limitations/built-ins of the game software); the In Character culture (the influence of the game win-state and incentives); and the Out Of Character culture (social interaction, morality).
There's more to say here than I can write down, but for the moment compare these: One. Popper's three worlds (objective, subjective, social; or: of-game, in-game, in-players). Two. The geography of a game (immutable laws of physics, or the board itself, depending on whether the "game" is a board-game or Real Life); the rules of a game (win-states and rules explicitly set by the game, eg get a line of three crosses, or take Berlin); the morality of the players (rules implicitly set by the game, that is, agreeing to obey the explicit rules, or declining to bomb civilians). Interesting.