Now for the why of it?
The fact that the article got changed after I posted this doesn't make it any less valid.
1) Who cares?
2) One perspective is that he was generous about sharing his opinion with HN. You, however, are accusing him of writing a DISHONEST REVIEW with the SOLE intention of MANIPULATING the reader into making a purchase.
3) Everyone is always selling something, you're selling a reputation of being the noble crusader of HN.
Incidentally..
1) For those who aren't as materially wealthy as you, a few dollars from an affiliate commission can be meaningful.
2) Aff link stats can be a useful metric of influence
In any case, as you can see from my tumblr blog (narekk.com) I do not write or post much. I may, however, post meaningful things in the future. HN readers gives great feedback.
Examples: the book is 288 pages but only 30,000 words; every other page is an illustration, and most pages are only 3/4 full; footnotes are rare, and usually reference some pop-biz online piece from Forbes or BusinessWeek.
The final chapter (on culture) was very good. It's a topic that doesn't require any rigor to be effective. But the rest of the book was actually one of the more disappointing reads of the last 12 months.
Edit: I'm sorry this is so negative. I really like 37sigs and Jason in particular. Maybe I had too high expectations?