You want to use the events On Op, On Help, and On Voice to give commentary about somebody's mode status when they receive it.
Also
if ($nick isreg $chan) msg $chan - Welcome, $nick Thank you for registering your nick!
This does not mean they are a registered user. It means they are a REGULAR user without any status at the moment. All users Join as "isreg" until you op, halfop, or voice them.