Thanks for resurrecting this post! I also appreciate the clear guidance that "a substantive article with a slightly baity title is not one that should be flagged". Maybe this could be added to the
https://news.ycombinator.com/newsguidelines.html?
I'm not sure, though, that it makes sense to focus on the idea that it was a "mistake" to flag this article. I think flagging is currently one of the weakest areas of the HN moderation system, in that it allows a minority to suppress discussion of otherwise good articles that they disagree with. Clearer guidelines can help, but I think you should also think hard about how the system can be changed to be more resilient to "mistakes".
Maybe flagging of articles with some minimum number of upvotes should act only as a "request for moderator review" rather than having any immediate visible effect?
Maybe there could be a way (either mandatory or optional) to explain why an article was flagged? I presume it would be easier to review a flag that says "Bad title, should be X" than just an opaque and universal flag.
Maybe there could be some better feedback for users who flag articles, to tell them if they are flagging articles "correctly"? As it is, I presume a lot of people persist in doing what they think is best, even if you think they are using the system incorrectly.
It's great that thanks to good moderation HN is still going strong after all these years. Obviously you are doing many things right! But I strongly feel that current flagging system needs to be rethought for this success to continue. Explanatory comments like the one you made here are helpful, but I think some deeper changes will also be necessary.