My feeling is that the traditional definition of self discipline is kind of a fake thing. To me, self discipline is knowing yourself well enough to know where you will fail, and taking appropriate counter measures - not being strong-willed or something.
As a matter of fact Jim Loehr and Tony Schwartz authors of "Power of Full Engagement" say that the idea of self-discipline (in the form of strong-will) does not lie at the base of productivity. Indeed they say that human being do not have near enough energy to be self-disciplined in that sense for many decisions.
I think that the real value of the article's tips is that as you get used to not going on HN/Reddit or just avoiding other types of procrastination you will get used to not doing that and thus won't do it even if you remove the barriers.
