If we have multiple accounts of same type, for example 2 gtalk accounts and if there is one contact who is added in both accounts, contact list shows contact twice and both show contact email in tooltip but there is no way to identify which account the contact belongs to. So it is difficult to use particular account for chat as there is no way to identify the account. Only way is to make other account offline :) Reproducible: Always
In 0.6, the tooltip shows the account, I'm not sure if we had this in 0.5 though. In 0.5 you can use the "Show Contacts by Account" button and see the contacts grouped by account. If this isn't enough please re-open the bug