Ok, since both top-level comments (to date) are saying that, and since that site hasn't appeared on HN before either, I've switched the URL to it from https://www.tripsitters.org/. Thanks!
TripSit is the quick summary for partygoers, Psychonautwiki is the encyclopedia for drug nerds. DMT-Nexus is the ancient club for mad scientists with hair growing out the sides.
To me it looks like a pretty weird decision to switch to a different project ON HN when someone is showing off a different implementation, even if one came first.
Would me posting a new search engine be switched to Google, as that came first? Or maybe a new internet archiving project to archive.org?
Your specific examples don't work because those projects are super well known. Switching to them would make the thread more generic, which is the wrong direction (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...), so we'd never do that. Indeed, a new search engine or internet archive would be interesting just by not being Google or archive.org.
But sure, we often change URLs to ones that are likely to support more interesting or better-quality discussion. That's part of curating the site. For an example of a common pattern, we often change corporate press releases to the best third-party discussion we can find about the story (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...).
In this case the signal was that the first two (presumably independent) subthreads said the same thing about the other site being more interesting, and that site had never been posted to HN before. That's a really unusual state and a strong community signal, one that seemed worth rolling the dice on. Listening to community signals is a big part of our job, maybe the biggest. In the end, this one didn't work out particularly well, but moderation is guesswork.
I agree with you that it was a weird decision. Another part of our job is to keep HN weird. It's not likely to become a common pattern, because that signal is a rare one to begin with (I'm not sure I've ever seen it come up before), and getting predictable about such things would be at odds with the global goal of maximizing interestingness. Curiosity withers under repetition (https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...), a bit like how a joke gets less funny as it gets repeated.
