Well, most players don't care. However in games with enough population you are likely to have role-playing guilds which will go to some trouble to role-play and yes, that involves the language used in chat (on the third tentacle there is always an OOC (out of character) chat channel where you can speak normally).

Gender-wise, everyone is assumed to be a guy -- unless (a) you explicitly declare yourself a girl; (b) you are on voice comms and your voice is clearly that of a girl; (c) you're in guild chat where people know that you're a girl.