Trying to use standards entities in a xdoc file for xhtml generation seems impossible now.
If I put the entities as is in the file, I get an error at site generation because the entity is not known to Doxia. I did not find any way to declare the few entities I use, and since the xhtml generated is ISO8859-1 encoded, there would be a problem afterwards because they do not belong to this encoding.
If I try to escape the '&' character, either by using ∇ or <![CDATA[∇]]>, the escape works well at site generation step, but is still there in the generated xhtml (on both cases I end up with &nabla.
I would like to have some intermediate behaviour, escaping a '&' from doxia parser but having it put verbatim in the generated xhtml file.
I am completely blocked here.