I want to point to Ragnhild Tronstad's exellent article on Semiotic and nonsemiotic MUD performance (pdf). She argues the distinction between theatricality and performance in MUDs, and she does so comprehensively and elegantly.
Using performance and theatricality as metaphors to describe MUD adventure games this paper starts out by defining a difference between ’performative’ and ’theatrical’ acts within MUDs. Performative acts differ from theatrical acts in that they are effecting ’real’ changes to the MUD environment, thus directly influencing the game in one way or another. It is argued that to understand the performative aspects of MUDs it is necessary to separate ’acts’ from ’meaning’, and to pay special attention to the former in order to avoid confusing the questing process (which should be our main focus of attention) with the experience of having solved a quest.