Oh, I didn't know that practice has been going on for that long. It's sort of become my pet-peeve as well, seeing as how the "war on clickbait" has resulted in moderators frequently changing perfectly good titles into bland three-word summaries that often do a worse job of representing the articles.
I think they're operating from a definition of "clickbait" that includes anything that makes a headline appealing, including any sort of pun or metaphor. There's nothing wrong with changing "Ten reasons MySQL is better than PG–and how switching may safe your Data". But it should be done sparingly, and default to respecting that the headline is also creative work, and deserves a bit of respect.
The worst example was http://ascii.textfiles.com/archives/5139. Halfway through, the post reveals that the author had a heart attack. Not mentioning it in the title was quite obviously a literary choice.
HN changed the headline, before changing it back, to something like "Jason Scott had a heart attack"
(but I guess I better shut up now :). I'd also like to mentioned that, with dead_posts=on, I've come across some seriously above-and-beyond work by dang. Just recently he was basically giving therapy to some guy posting wild rants in low-contrast posts at the bottom of some thread. )