I think what you're looking for is in the postbit template.
There is a certain section that is a bit over halfway through that looks like:
Code:
<if condition="$show['postedited']">
<!-- edit note -->
<div class="smallfont"> <hr size="1" style="color:$stylevar[tborder_bgcolor]" />
<em>
<phrase 1="$post[edit_username]" 2="$post[edit_date]" 3="$post[edit_time]">$vbphrase[last_edited_by_x_on_y_at_z]</phrase>.
<if condition="$post['edit_reason']">$vbphrase[reason]: $post[edit_reason]</if>
</em>
</div>
<!-- / edit note -->
</if>
Seems to me if you remove that entire section of code then no edited remarks will show up. Not 100% sure, but it looks like that should do the trick.