The ability to correctly identify the existence and polarity of emotion in informal, textual communication is a very important part of a realistic and immersive 3D environment where people communicate with one another through avatars or with an automated system. Such a feature would provide the system the ability to realistically represent the mood and intentions of the participants, thus greatly enhancing their experience. In this paper, we study and compare a number of approaches for detecting whether a textual utterance is of objective or subjective nature and in the latter case detecting the polarity of the utterance (i.e. positive vs. negative). Experiments are carried out on a real corpus of social exchanges in cyberspace and general conclusions are presented.