Problem using squelch_replies in rt 1.0.7

I’ve tried to figure out how to use the squelch_replies variable as best
I can by looking at the perl in:

lib/rt/ui/mail/manipulate.pm

…but I can’t seem to get it right. If I have an established ticket, and
I send e-mail to my RT mail alias with the correct [identifier #num], a
copy of that e-mail is sent to the “requestor” of the ticket. I don’t want
that to happen.

I’ve made the following changes (sorry these aren’t diffs):

elsif ($in_action eq ‘correspond’) {

  #If we're creating a new ticket
  if (!$serial_num) {
      # no auto-reply on ticket creation.
      $squelch_replies = 1;

…and…:

#If we’re corresponding on an existing ticket
else {
#If the user isn’t a requestor, notify the requestor
#knock that off!
$squelch_replies = 1;

Am I missing something here, or is there something else I have to do in order
to disable the behavior I described above? The first modification I made
works; the second one has no noticeable effect.

Even if I comment out the following line:

$notify_requestor = (&rt::is_not_a_requestor($current_user,
$serial_num));

…the mail still gets sent out.

This is very frustrating for me, as, to all appearances, I’m in the right
area to make this modification. Can anyone help?

Thanks much,

–Kyle
UCO/Lick NICS