Hi Grundgütiger,
go to the console and enter:
grep -r 'overlay-social-open' /var/www
/var/www/app/templates/playback.php: <button id="overlay-social-open" class="btn btn-default" type="button" title="Share this track"><i class="fa fa-share"></i></button>
/var/www/assets/js/runeui.js: // var triggerBttn = $('#overlay-social-open'),
As you can see it is in "/var/www/app/templates/playback.php".
Delete / comment this line and the button is gone.
Frank
