In certain combinations with italic inline elements, space between words is dropped, creating run-ins. For example,
<para>blah <literal>blah</literal> <replaceable>blah</replaceable> blah</para>
blah blahblah blah
This bug was introduced in 1.78.1 in this commit: http://sourceforge.net/p/docbook/code/9703/
For a full example, see the attached test document and process with
xsltproc http://docbook.sourceforge.net/release/xsl/1.78.1/manpages/docbook.xsl test.xml
The commit says that it fixes some other bug, but I can't find it because SourceForge has renumbered everything. I suggest that it be reverted, though, because the current issue seems pretty severe.