Optimizing means trading other things away. One thing we're willing to trade away–if it's a clear win for quality–is fidelity to the original submission. HN's focus should always be on the content, and the details of the original submission are of little interest compared to the subject at hand.

Was this particular change a clear win for quality? Well, the new link was better, as was the related subthread, which even included the author of the content, who even served on the relevant IEEE committee, and who was even game to politely bandy about design decisions with strangers superciliously claiming (in the internet's own special way) that he and his colleagues had done their work badly. It's pretty hard to get higher quality than that.

HN isn't a purist's kind of place. Our goal to make the front page and the threads as interesting and substantive as possible. We change a lot of things to serve that principle. If we knew how to serve it better, we'd happily break more crockery.

Someone (perhaps a purist!) will object that terms like "quality", "interesting", and "substantive" have no precise definitions and are in the eye of the beholder. True, but (a) they're not arbitrary either, (b) the alternatives suck, and (c) someone has to make the calls. We don't get them all right, but we do try hard to correct mistakes, and I'll defend the principle any day.