MUD players are in complete control over how they are looked upon in the textual world. By using the [@describe] command, MUDers literally define themselves. There is no set format or guideline for what should be included in these descriptions. While most stick to physical traits (of a fictional self), players use the descriptions to say things about character that physical appearance would fail to relay. When other characters encounter them and type [look], they will see the description that the player has written.
In real life, there are all kinds of unintended visual and aural cues accompanying encounters which may or may not reflect accurately on character. Prejudices of the real world may impede an intellectual woman to be taken seriously by some men, for instance. In the MUD, such a person can set their gender to male and converse for a while. Or they could leave gender undefined or neuter. Because self-authored text is the only information representing MUD personae (even name is chosen by players), players have full control of the self they present to the virtual world.