Additionally to what Jtsummers said, quoting on desktop can drastically reduce the line length compared to the rest of the lines in the comment, which is both ugly and annoying, especially since it makes it more difficult to read since your eyes are whipping back and forth.

There are a multitude of mobile apps for consumption of HN, most of which solve the code-block-line-overflow problem by adding a horizontal scroll, which only makes the problem worse by forcing users to scroll side to side to read the full quote.

Just use `>` at the start of the line to signify that it's a quote, please.