We are working on a niche domain, i.e. colour science, and the team was undoubtedly happy with the achievement. This morning, I noticed that the thread is flagged, which is mildly saddening:
https://news.ycombinator.com/item?id=24625977
When did people start to flag development successes? When did celebrating become not desirable? Celebrating success stories is an integral part of what makes HN.
AFAIK, talking about Github stars has never been an issue here: https://hn.algolia.com/?dateRange=all&page=1&prefix=true&query=%22github%20stars%22&sort=byPopularity&type=story
I have been on HN, mostly lurking, for over a decade, and I have certainly always enjoyed reading about other development projects celebrating their achievements. Seeing other developers happy and joyful is a motivation factor for our work.
I'm guessing that there was some difference between your original post and the ones you're comparing it to that is causing it to be perceived badly. You should reevaluate your submission, see if there's anything that might be breaking any of the site's guidelines, then edit it and resubmit.