Online help

Choosing all identities allows you to chat in the conference you are creating with everyone in your address book regardless of which of  your identities each person knows you as. Be aware that if you have identities which you use to have anonymous contact then you would not want to make this selection.

After you have made your identity choice the Chat window is displayed.

The alternative is just using just the Identity you are known as to that person.

Online presence identity is not affected
Using All identities in a Chat window is different than being online as all your identities.  You can also choose to be online as one or several or all identities using the Chat Prefs panel after choosing Prefs from the opening screen.  This determines what other Ezian users see whenever you are online.  They will see you as online as those identities you have specified in Prefs.  This allows those users to invite you Chat to chat with them. If you don't wish recipients you know you by a certain identity to invite you to chat, then you choose to show that identity as offline in Chat Prefs.