Consider the following document:
<article lang="en"> <title>Language Test</title> <para lang="de">Dies ist ein deutscher Absatz.</para> <para lang="ar">هذه هي الفقرة العربية.</para> </article>
Transforming the above document with version 1.78.0 into XSL-FO leads to the following fo:block structures:
<fo:block space-before.optimum="1em" space-before.minimum="0.8em" space-before.maximum="1.2em">Dies ist ein deutsches Zitat</fo:block> <fo:block space-before.optimum="1em" space-before.minimum="0.8em" space-before.maximum="1.2em"> هذه هي الفقرة العربية.</fo:block>
As you can see, language and writing-mode attributes are missing. The same situation applies, when you use sect1 or other structural elements.
For reference, see discussion on the docbook-apps mailinglist:
https://lists.oasis-open.org/archives/docbook-apps/201410/msg00005.html