I think I understand what you want, take a look at this:
PHP Code:
$karmas=$DB_site->query("SELECT karma.postid as postid,karmapos,karmaneg,reason,post.threadid as threadid,post.dateline as dateline,thread.title as title,whoadded,user.username
FROM karma, user
LEFT JOIN post ON karma.postid=post.postid LEFT JOIN thread ON post.threadid=thread.threadid
WHERE karma.userid='$bbuserinfo[userid]' AND user.userid='$bbuserinfo[userid]'
ORDER BY timestamp DESC LIMIT 0,5");