Only if you don't hit the post button.
If you change your mind about posting something before hitting post you don't need to delete anything - you can move to another section or simply close the browser or computer and no evidence that you ever intended to post will show because you didn't post - clicking the post button makes a post.
Once the post button has been hit there will be a post recorded. You can delete the content of it right down to a single character but you cannot delete the post. Just as cheddar-caveman and countless others including me have found.