Okay, so this was in a high need of a recode.
First of all, with the method I used above it replaced 'm' with 1000000
That works in some cases, but if you have !calc 1m/1m it returns 1,000,000,000,000 instead of 1.
So I turned it into regex, making it do something like $calc((11000000)/(1*1000000))
However this wasn't capturing the . so I made another edit to incorporate that.

...then I made it one line xD

Old script for history to anyone who's interested, editing the new script above now.

alias -l comma {
  var %a, %b = $regsub($ticks,$1,/\G([+-]?\d+?)(?=(?:\d{3})++(?=\.\d++$|$))/g,\1 $+ $chr(44),%a)
  return %a
}

on *:text:!calc*:#: {
    if ($1 == !calc) {
      if ($2-) {
        if ($chr(37) isin $1-) {
          msg $chan You cannot use percent in this calculator, sorry.
        }
        else {
          if ($remove($2-,k,m,b,$chr(44),.,+,-,/,*,^) !isnum) msg $chan Sorry $nick $+ , I can't calculate words.
          else {
            var %calc1 $comma($calc($replace($2-,k,*1000,m,*1000000,b,*1000000000,$chr(44),$null)))
            timer 1 1 msg $chan 4Calculating: 03 $+ $2-
            timer 1 2 msg $chan 4Result: 03 $+ %calc1
            if (%calc1 == 0) {       
              timer 1 5 msg $chan If 0 is not the correct answer, that is because this calculator can't handle some or all of the characters used or the formula used.
            }
          }
          else msg $chan I can't calculate nothing...
        }
      }
    }
  }