It seems that when a talk page that you've got on your watchlist is Flowified, the new Flow page is no longer on your watchlist.
See this for the original report: https://www.mediawiki.org/w/index.php?title=Talk:Beta_Features/Hovercards&topic_postId=rrdxogy40i5l8am5&workflow=rrdxogy0w9aajx6l#flow-post-rrdxogy40i5l8am5
I am, obviously, unable to verify this at this stage without getting another page Flowified.
Version: unspecified
Severity: normal
I tested on my local machine and it worked as expected: page is still watchlisted after enabling Flow on it, and I see the newly-posted Flow topic.
There must be something else going on, I guess - I can't remember any recent work that would have fixed this.
Can another dev test if it works for them?
(In reply to Matthias Mullie from comment #1)
I tested on my local machine and it worked as expected: page is still
watchlisted after enabling Flow on it, and I see the newly-posted Flow topic.
Indeed, there's a report from another user that when the Hovercards talk page was Flowified it remained on their watchlist.
I'm unsure what's going on, too.