It's a long line of text. HN puts monospace text in a fixed-width container, so you need to scroll right inside the box to see the rest of it.

Ugh. It's like Slashdot with its interface where you need to hover. How do do you hover on a mobile? I don't visit Slashdot much any more, because most of my surfing is on mobile. And I won't be scrolling little windows of monospaced text left and right, left and right, over and over, any time soon.

There's a horizontal scroll bar :)

I'm not sure how to format a block quote without it.

Edit: Well, just added newlines. Seems to look ok.

Don't use leading spaces, just use >

Or do use leading spaces, but insert line breaks. Remember that people on mobile have very short screens.

Scrollbars are invisible in my mobile browser until I scroll the box. It just looks like a badly-formatted quote. Something to keep in mind if you're a ddveloper.