I'm not sure if this is sarcastic or not, but the problem is when the quoted text is longer and/or multiline, and especially when it's both.
You typically see users working this around with spacing, and (sometimes) other users complaining (rightfully) that they can't see the full text on mobile without scrolling.
This is exacerbated by the fact that then HN rendering only has the "<p>" concept, not the "<br>". If one works this around using the greater than symbol, and there are several entries, it blends too much with user-typed text.
It's not a very big deal, but it's pretty much standard feature in forum engines, and the lack of it makes the text outlook unnecessarily worse.
Exactly