a few things could be shortend

if (%sl.qra == $null) { msg $chan 10,0Random quote 6# $+ %sl.qr 10 $+ %sl.qra  }

Could be

if (!$sl.qra) msg $chan 10,0Random quote 6# $+ %sl.qr 10 $+ %sl.qra 

    set %sl.qr $rand(1,$lines(quote.txt))
      set %sl.qra $read(quote.txt, %sl.qr)

This could be set to the var command so you dont have to unset them after, and when unsetting variables that start the same, unset sl.* works.

And finally

  else { halt }
}

no need for the else, just end it off.