I've just noticed that <note> (and likely <caution>, <warning>, and <tip>) especially when having a <title> generate semantic HTML garbage HTML. See e.g. https://www.php.net/manual/en/openssl.installation.php.

<note> yields a <blockquote> which is doubtful per se, but the <title> is just a <strong> element. Instead, we should probably generate a <section> (a div might be a first step in the right direction) ideally with a proper heading for the title. Regarding the latter it might be hard to keep a proper heading structure, but even a gap in the headers appears to be better than misusing a <blockquote>, and a title should be a title.

Also, <simpara>s inside the <note> are apparently ignored/collapsed.