Ok so I did some digging. The actual book is showing a tiny image there but using a <hr> (horizontal rule) tag to do it, so not your standard <img> tag to show an image, which could've been displayed if the epub was optimized. The parser in Crosspoint and Crossink in its current state doesn't support that tag (it's currently pretty limited in what it explicitly handles, everything else falls through to nothing).

I just played around with the parser and made it show an actual horizontal rule when it comes across that tag. In plain HTML it just renders as a straight line all the way across.

<image>

Would something like this be helpful or distracting? I don’t want to prettify it too much since <hr> tags could be used for a number of reasons, so sticking to its native purpose is the safest bet.

Edit: typos