Not seen - yet - an option to mark a posting as 'spam'. There is something however to mark as 'abusive'.
I've just marked a couple of 'spam' items using this option, and I'll see what happens. OK, the items are not 'abusive' as such, but YES, they are an abuse of the forum.
The longer such items sit there, the happier the poster will be. Robot or otherwise. The quicker they vanish, the better.
The message, I mean. Oh, all right, yes, the poster as well!!