The first feature is iChat’s support for the “/me” command from IRC (Internet Relay Chat). If you start an iChat message with/me, then anything you write after that will appear, after your name.
The second iChat feature is the very simple but somewhat hidden capability to find the timestamp on any chat message. iChat will, on its own, stick timestamps into your conversations at various times. But what if you want to tknow the exact time—to the second, even—that you sent or received a certain message?
To see any given message’s timestamp, simply hover your cursor over any portion of the message (it must be over the text in the message, not the icon next to the message or the box that contains it). In a second or two, a floating tooltip will appear, showing both the date and exact time that particular message was sent or received.