When the admins get to it. There aren't that many.
Things get removed faster if a moderator sees it and thinks it should be. The deeper it's buried in some comment-conversation, the less likely that is, because nobody is reading that shit once it goes on for a while.
That all depends. After you flag said comment or post the administrators review it and decide if it is offensive , if it is they will remove it pretty quickly. How ever if they find that it doesn't fit into their offensive criteria then it will not be removed