Right now when you set module_config entries in your pillar data
like this:
salt:
  minion:
    module_config:
      smtp.from: 'Kali Salt <admins+salt@kali.org>'
      smtp.to: 'Kali Admins <admins+salt@kali.org>'
      smtp.host: localhost
      smtp.subject: 'Results of salt actions on'
      smtp.fields: id,fun

On each run, you will always a different ordering of the various
fields in the minion configuration file, leading to spurious restart
of the minion and admin annoyance:

          ID: salt-minion
    Function: file.recurse
        Name: /etc/salt/minion.d
      Result: True
     Comment: Recursively updated /etc/salt/minion.d
     Started: 13:39:25.689775
    Duration: 874.318 ms
     Changes:
              ----------
              /etc/salt/minion.d/f_defaults.conf:
                  ----------
                  diff:
                      ---
                      +++
                      @@ -930,10 +930,10 @@
                       # A dict for the test module:
                       #test.baz: {spam: sausage, cheese: bread}
                       #
                      +smtp.fields: id,fun
                      +smtp.from: Kali Salt <admins+salt@kali.org>
                       smtp.to: Kali Admins <admins+salt@kali.org>
                      -smtp.fields: id,fun
                       smtp.host: localhost
                      -smtp.from: Kali Salt <admins+salt@kali.org>
                       smtp.subject: Results of salt actions on

With the change here, this bad behaviour is gone...