I appreciate the author's point, but it's not like selling the diploma prevents him from saying he went to Harvard, nor does it allow the purchaser to claim that they did themselves..
If the author had just shredded the document and written a generic article about prestige without mentioning his associations, I fear that title would do less well.
But yeah I agree with your point that buying/selling a piece of paper doesn't transfer the knowledge, friendships, networks that one can build in college.
Which in my experience is something that people who went to these institutions will do, constantly. Goes down incredibly well in countries where the the idea of tiers has yet to catch on.