on NICK
The on NICK event triggers when a user changes nickname while on the same channel as you.
Format: on <level>:NICK:<commands>
Example: on 1:NICK:/echo $newnick was previously known as $nick
on *:nick:{
if (!$window(@Nick)) { window -e @nick }
echo -t @nick $nick is now $newnick
}
This event doesn't give the channel name but you can use $comchan($nick,1) or something if you want to show what channel you both are in.