Hi,
Actually, your situation is not how it is by default in HikaShop.
The user email is not used for the username of the user accounts by default instead you change the "registration" setting of the HikaShop registration to "simplified registration" which removes the username field.
And we actually use the username of the user account instead of the user's name in order to prevent the display of the user's name in the comments so that only his username (which can be anything) appears in order to protect his privacy.
Now, if you want to keep the way it works with the registration and only replace the vote_pseudo display on the listing of comments by the name of the user, you can edit the file vote/listing.php via the menu Display>Views.
There, you'll see:
<?php if ($elt->vote_pseudo == '0') { ?>
<span itemprop="name" class="hika_vote_listing_username"><?php echo $elt->username; ?> </span>
<?php } else { ?>
<span itemprop="name" class="hika_vote_listing_username" ><?php echo $elt->vote_pseudo; ?></span>
<?php } ?>
which you can replace by:
<span itemprop="name" class="hika_vote_listing_username"><?php echo $elt->name; ?> </span>