This is off topic, but I don't think the problem is just that the Twitter is terrible.
If you want to link to a thread, you should click on the first tweet of that thread and copy its url. It's easy to see the rest of the thread: just scroll down.
If you want to link to one tweet in a thread you should click on that tweet and copy its url.
The person who posted the link to HN did the latter, while they should have done the former.
Twitter could make it easier to see that a tweet is part of a thread though.
While we're off topic here's my little rant about Twitter "threads":
It's easy to see all of the tweets made by the author, at least those made as replies to themselves, but reading the actual threads is hard or impossible. At least I haven't figured out how to do it despite considerable effort.
For example, say you want to view the replies to the tweet above the linked tweet, the one about "assert". There are supposedly 4 replies. If you tap that tweet you remain in the same list of self-replied tweets. There are replies at the end, but are they replies to the tweet you want to focus on? It doesn't look like it, but who knows, maybe? It's even worse on linger Twitter self-reply "threads".
I don't know how Twitter's engineers got the well-established threading pattern so wrong. This behavior doesn't even increase the number of ads you see.
I was so sure I copied the first tweet to submit. That is why the title is the same as the first tweet. Somehow I messed it up. May be Dang could change it to
I'm glad the terrible "defer" suggestion didn't make it, but unfortunate that they didn't standardise the existing and widely used attribute cleanup.