There are two ways to fix this bug. The css way, and the html way. I chose the html way.
This patch simply observes the type of numbering demanded by the apt list ([[i]] for example), and writes the corresponding 'type' attribute on the ordered list.
The css way would be to write a class attribute instead, and then add corresponding styles in maven-base.css (or whichever stylesheet is the correct one). We could also do an inline style:
<ol style="list-style: lower-roman">
Both CSS solutions are much more flexible, but it looked like the XhtmlSink was designed to use the predefined html types, hence this quick solution.