As a workaround for
Revo 2.1.2 you could edit line 111 of the file [tt]\core\lexicon\en\default.inc.php[/tt] - change
$_lang['duplicate_of'] = 'Duplicate of [[+name]]';
to
$_lang['duplicate_of'] = '[[+name]]';
EDIT:
In Revo, if you choose the option "Duplicate Resource" out of the context menu you get by a right click on the resource in the tree, you are asked for the new name in an empty input field. That works even without editing the mentioned file.
But in this case you explicitely have to open the created duplicate to edit it, which is certainly not practicable if you have to duplicate lots of resources.
In
Evo 1.0.5 you find the string to edit in line 65 of the file
[tt]/manager/processors/duplicate_content.processor.php[/tt] :
$content['pagetitle'] = 'Duplicate of '.$content['pagetitle'];
Check the other files [tt]/manager/processors/duplicate_xxxxx.processor.php[/tt] too.