Just learned #identd because some #ircnet servers think it helps anything when they force people with certain IP addresses, which they identify as "VPS", to enable it.
TL;DR: With identd running on the client, the server can ask which user has opened the connection by mapping the source tcp port to the user.
The identd's client answer, of course, can be spoofed when you are the administrator of the client machine. So I don't understand what this is all about.
