Hmmm. I modified it like so, but it’s still showing the third item twice, once in the first div and once in the second.
<div class="column-left">
<?php $count = 1; while (have_rows('features')) { the_row(); if ($count > 1 && ($count % 2 == 1)) {?>
<div class="item">
<h6><?php the_sub_field('title'); ?></h6>
<p><?php the_sub_field('description'); ?></p>
</div>
</div>
<div class="column-right">
<?php } ?>
<div class="item">
<h6><?php the_sub_field('title'); ?></h6>
<p><?php the_sub_field('description'); ?></p>
</div>
<?php $count++; } ?>
</div>
</div>
