When do we delete comments?

You may have noticed a few instances on this blog where comments to a posting have been deleted.  Up to now, all of the deletes have been spam.  Spammers put up ads which we surely delete.  Those spammers who are a wee bit cleverer will put up a comment that says something like "what a great post" and then include a link to their websites.  

If you are a spammer and happen to be reading this post, kindly get outta here: