Keyword Stuffing is an outdated, damaging practice. I'm not sure how effective it ever was, but I do know that just about every manager, owner, and webmaster who begins learning about SEO writing, comes up with it and tries it out.
My basic policy with this particular topic, and others like it, is 'I don't do it.' Really it is that simple. You've read in this article and many others I have written, that most of the decisions for Freelance Writing are on the client. But this is one of the areas which I don't leave to the Client, because along with today's payment, is tomorrow's payment, and I would rather loose one client than loose several others because of reputation and complaint.