In some cases it may be useful, for a teacher, the notification, by email, of student self enrolment in one of his courses.
I developed the attached patch following the idea that moodle uses for grades.

The project I had in mind was:

inside Courses->Enrolments->Internal Enrolment->Edit, I added one more drop down menu. It is show_selfenrolment.

IF (!empty($CFG->show_selfenrolment)) {
into each course editing settings page it is shown the new drop down menu "Notify self-enrol by email".

If this second drop down menu is set to Yes, then at user selfenroll time an extra email is sent from teacher to himself to notify the user self-enrol.

This is the list of patch I made available.
accesslib.patch that has to be applied to moodle19/lib/accesslib.php
config.patch that has to be applied to moodle19/enrol/manual/config.html
edit_form.patch that has to be applied to moodle19/course/edit_form.php
enrol_manual.patch that has to be applied to moodle19/lang/en_utf8/enrol_manual.php
enrol.patch that has to be applied to moodle19/enrol/manual/enrol.php
install.patch that has to be applied to moodle19/lib/db/install.xml
moodle.patch that has to be applied to moodle19/lang/en_utf8/moodle.php
moodlelib.patch that has to be applied to moodle19/lib/moodlelib.php
upgrade.patch that has to be applied to moodle19/lib/db/upgrade.php
version.patch that has to be applied to moodle19/version.php