I've answered my own question with some more reading and some messing around...

I had to run a 'foreach' that cycles through the given post's comments within the main loop. 

The following code looks at all the comments for each post that passes through the loop and checks for a specific string in the comments' content. Depending on if $findme is matched, a specific HTML ID is written to the div. At a glance, one can see which posts contain specific content in their comments. Party on.


    <?php
    if( have_posts() ) : while (have_posts()) : the_post(); ?>
    <div id="post-<?php the_ID(); ?>" <?php post_class('col-md-6 box');?>>
    <div class="post-box article"  

    <?php

    $comments = get_comments( array( 'number' => 99, 'post_id' => get_the_ID() ) );

    if(get_comments_number()==0) : ?>
     		id="pendingcomment"
    <?php else : 
	
    	foreach($comments as $comm) :
    		
    		$mystring = get_comment_text( $comm );
    		$findme   = 'CHANGES!';
    		$pos = strpos($mystring, $findme);
		
    		if($pos == true) : ?>
    			id="notapprovedcomment"
    		<?php elseif($pos == false) : ?>
        			id="approvedcomment"
    		<?php endif; 

    	endforeach;
    endif; ?>
    >

The code could no doubt be cleaner, but is functional.
Hope someone finds this useful one day.