editpost.tpl

find:
Code
<input type="hidden" name="gallery" value="{$is_gallery}" />

add below:
Code
<input type="hidden" name="markedit" value="1" />

find:
Code
<input type="checkbox" value="1" id="markedit" name="markedit" checked="checked" class="form-checkbox" /><label for="markedit">{$lang.MARK_EDIT}</label>

send it to the dustbin..

quick/dirty *poof*