To only show the DIV.privacy box if either the survey is set to be anonymous (this will cause Limesurvey to show a default privacy note) or if the user selected to show a custom privacy message, the following adjustment can be made at privacy.twig:
{#
LimeSurvey
Copyright (C) 2007-2017 The LimeSurvey Project Team / Louis Gac
All rights reserved.
License: GNU/GPL License v2 or later, see LICENSE.php
LimeSurvey is free software. This version may have been modified pursuant
to the GNU General Public License, and as distributed it includes or
is derivative of works licensed under the GNU General Public License or
other free or open source software licenses.
See COPYRIGHT.php for copyright notices and details.

(¯`·._.·(¯`·._.· Privacy ·._.·´¯)·._.·´¯)

Show the privacy message (in All in One Mode)
see: allinone_mode_welcome_privacy.twig

#}

<!-- Privacy message -->
{% if (aSurveyInfo.anonymized == "Y" or aSurveyInfo.showsurveypolicynotice == 1 or aSurveyInfo.showsurveypolicynotice == 2) %}
<div class="{{ aSurveyInfo.class.privacycontainer }} row" {{ aSurveyInfo.attr.privacycontainer }}>
<div class="{{ aSurveyInfo.class.privacycol }} col-sm-12 col-centered" {{ aSurveyInfo.attr.privacycol }}>
{% block anonymous %}
{% if (aSurveyInfo.anonymized == "Y") %}
<div class="{{ aSurveyInfo.class.privacyhead }} h4 text-primary " {{ aSurveyInfo.attr.privacyhead }}>
{{ gT("This survey is anonymous.") }}
</div>
<div>
<p class="{{ aSurveyInfo.class.privacybody }}" {{ aSurveyInfo.attr.privacybody }}>
{{
"The record of your survey responses does not contain any identifying information about you, unless a specific survey question explicitly asked for it."
| t
}}