It's not a <pre> tag, it's an automatic format that HN applies to indented text. That's why indenting is not the preferred way to show quoted text. I use quotation marks to show text quoted from a submitted article, and the HN convention of an asterisk immediately before and after a block of text quoted from the parent comment (as above, here) to show text quoted from a comment.

  pre { white-space: pre-wrap; }

javascript: document.body.innerHTML=document.body.innerHTML+"<style>pre { white-space: pre-wrap; }</style>";

(Sorry, double comment, I think I messed something up while messing with this. Also, it kills most of the current style. Anyone have a better variant? Might be good to have as a bookmarklet.)