Don't treat objects like strings.

modules/g2_import/helpers/g2_import.php

@@ -611,11 +611,9 @@ static function import_tags_for_item(&$queue) {
                array("id" => $g2_item_id, "exception" => $e->__toString()));
     }
 
-    $tags = "";
     // Multiword tags have the space changed to dots.s
     foreach ($tag_names as $tag_name) {
-      $tags .= (strlen($tags) ? ", " : "") .
-        tag::add($g3_item, $tag_name);
+      tag::add($g3_item, $tag_name);
     }
 
     // Tag operations are idempotent so we don't need to map them.  Which is good because we don't
@@ -634,11 +632,10 @@ static function import_keywords_as_tags($keywords, $item) {
       $delim = " ";
     }
 
-    $tags = "";
     foreach (preg_split("/$delim/", $keywords) as $keyword) {
       $keyword = trim($keyword);
       if ($keyword) {
-        $tags .= (strlen($tags) ? ", " : "") . tag::add($item, $keyword);
+        tag::add($item, $keyword);
       }
     }
   }