on *:INPUT:#: {
IF ($1 ison $chan) { HALTDEF | MSG $chan $+(,$left($1,1),,$right($1,$calc($len($1) - 1)),$chr(58)) $2- }
}
ok, I know it looks a bit difficult, but it just puts the first character of the nickname ($left($1,1)) between underline control codes (Ctrl+U), then adds the rest of the nickname ($right($1,$calc($len($1) - 1))), and finally it adds a : ($chr(58)).
You're right, but Iori's is more practical because if a user has a single character for a name, the script won't go "fubar" for a lack of better terms. It will remain uniform with the other posts.