Notebook titles are currently not trimmed sufficiently, allowing for inclusion of line breaks. This may not necessarily pose a problem, but suggests improper sanitization.
The RSS feed Recently published | Observable contains the following lines:
</item><item>
<title>
Ji</title>
<link>https://observablehq.com/@elisk/ji/2</link>
<description><![CDATA[<a href="https://observablehq.com/@elisk/ji/2"><img src="https://static.observableusercontent.com/thumbnail/f491c454e511b93c69b3f0cafa770bbfbe008fef454478c11ba191c49edec7a8.jpg" width="320" height="240"></a>]]></description>
<guid>https://observablehq.com/@elisk/ji/2</guid>
<pubDate>Fri, 23 Aug 2019 20:26:23 GMT</pubDate>
</item><item>
Line breaks can also be seen in the API document stub:
