I have reduced the font size to very small here but large interline gaps remained. Additionally, it does not seem to be monospace since length does not increase monotonously as it should in case of font-family: "Courier New",Courier,monospace. In edit mode, everything is fine.
Ok, the problem was that switching from HTML to WYSIWYG composition mode, blogger does something to the HTML so that
font-family: "Courier New",Courier,monospace; font-size: 1px; slipped into
<pre> tag where nothing more but font size had effect.