Yes, sorry, you're right. Both are mistakes, but as I didn't knew about that bug. The correct stuff is:
qa_report_event("u_mentioned", qa_get_logged_in_userid(), qa_get_logged_in_handle(), qa_cookie_get_create(), array(
"userid" => $value,
"questionid" => $questionid,
"postid" => $postid,
"post_type" => strtoupper($type[0]),
"time" => time()));
Which means that "postid" is "postid" and $time is time(). Probabily this bug just shows up now because Q2A should have a specific page where it inserts the comments, and then redirects to the question page. Thanks for reporting. :)