Yes, i have read that article. Here is my humble opinion: Having 80% of the expressibility, even if you don't need the other 20% that often, does not make you lisp. Which is why the title is not "Why ruby is lisp", but uses the word "acceptable". Its just semantics, and i don't want to argue about what makes something lisp, it wasn't even my main point.
I think "Why Ruby is Good Enough" makes for a better title, I'd agree. I don't think Ruby is Lisp either, I just felt that it went along with your point, that's all.
That is a good question, and worthy of an upvote. My first inclination is to say it is not, because if Ruby really were the "worse" to Lisp's "better" in some measurable, objective sense, then presumably Matz would have created something like Clojure rather than Ruby.
You may or may not agree, but you'll probably be interested in Why Ruby is an acceptable Lisp: http://www.randomhacks.net/articles/2005/12/03/why-ruby-is-a...
Covered on HN previously here:
http://news.ycombinator.com/item?id=416589