I just tried again, still didn't show any children. Then I did a force-refresh. Now it shows them ...
So due to past terrible performance of lkml.org, it had aggressive long-term caching. So since I happened to see this message a couple days ago, it wasn't showing a newer version of the reply tree for me, I only found them in the top-messages list on the lkml.org main page.
I've always found it really frustrating that lkml.org seems to be the canonical web link that comes up for kernel mailing list discussions because of this, as I really find the threading there frustrating; it's nearly impossible to determine whether you've read the entire (sub-)thread.
Back when Gmane was alive I usually gravitated there as an alternative.
Suggestions (or working links to what you like better) are welcome!
In particular I'd like to be able to, starting with a particular post, repeatedly hit "next" and be assured that once I hit the next sibling post to the original I've read that entire subthread. Gmane let you do this just by whacking the space bar; if you weren't at the bottom of a post it would page down, if you were it would go to the next one.
In other words I'd like it to behave as much like a good NNTP newsreader as possible.
That's lost technology from the golden age of our ancestors, who were so much greater than any of us now ;-)
Today this innovation has moved to the myriad of proprietary alternatives (like Slack or our very own HN) but they are closed worlds so not only can nobody create a new client, we also loose all the contents if the company dies (which isn't rare).
--grumpy greybeard
there is plenty of active usenet groups, comp.arch being one of the best places where the greybeards meet.