For me (on desktop) it looks like a list of tweets, one after another, sometimes with a "Load more of this thread" link in the middle.
In general I don't click twitter links on HN because I find the format painful for anything but short content. However I do make an exception for Foone as they have a lot of interesting stuff.
[0]: https://twitter.com/Foone/status/1372945388664066061?s=20
*they have
https://threadreaderapp.com/thread/1387999563382857729.html
I mainly don't want the rest of Twitter added into my experience or life, so this helps immensely.
I would've assumed that's the one universally reviled thing in the world (awkward stuttery twitter threads, as opposed to just an article/blog), but my assumptions are challenged again (always a good thing :).