Just ... Scroll ... Down ... Click where it says "read more" or "show more replies"
You're human; THE most adaptable creature known. Adapt!
I'm not saying that twitter UX is perfect, or even good. I AM saying that it is usable.
That doesn't work. Neither "read more" nor "show more replies" appears on the page [1]. Nor does "show replies", which turns out to be what you actually need to click once you go to a place it appears. In fact, there's no indication that there even are more replies, or that "replies" are actually the main content.
To see the content, it turns out you need to click on the original "1/" tweet, which takes you to what looks like a new page (but doesn't change the URL, so you can't link to it).
It is not usable in any real sense. I only spent the time to solve the puzzle as I was trying to make sense of your comment.
[1] https://imgur.com/a/BL9M74m (the centre column is shown in full, and there's nothing down further)
I think you are using a more extreme definition of "usable" than most people.
Originally, I clicked on the link, saw there was almost nothing there and no visible way of getting more, and went looking for a usable mirror in HN comments.
I'm 41. I'm not a paraplegic, but I am physically disabled; I've spent most of my adult life unable to use keyboards, for example, and there are many ordinary things that most people take for granted that I simply can't do. I think I have a fair and reasonable definition of "usable".
That's not what I'm saying. Not even close. However, if you knew even a small number of the usability issues that certain people are forced to put up with every day of their lives, you'd cease viewing twitter UX as a problem worth even acknowledging.