Hi Chris,
That is not necessarily so as you can add this in the PHP markup in the layout/includes/iconnav.php file like so...
<?php if ($PAGE->theme->settings->nav4icon) { ?>
<a href="<?php echo new moodle_url($PAGE->theme->settings->nav4buttonurl); ?>"
target="_self" id="button" data-toggle="tooltip" data-placement="bottom"
title="<?php echo $PAGE->theme->settings->nav4buttontext ?>">
<i class="fa fa-2x fa-<?php echo $PAGE->theme->settings->nav4icon ?>"></i></a>
<?php } ?>
Where new moodle_url = $CFG->wwwroot
This is how I was taught to do this. Also some words 'language strings' you add in the settings page should technically be a string so that it can get translated. For example: 'Home' or 'Calendar' should be get_string('home', 'moodle') or get_string('calendar', 'calendar') most words of this nature are already translated so knowing this its easy to add.
On the other hand the 'fa' font icon names are different as these are, in effect' code names and NOT strings.
I'm surprised no one pulled you up on that when the theme was originally reviewed.
Hope this helps?
Mary